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Engystoma Texense, Girard — Part 2
The skin of the back is loose and leathery, so that it can be thrust in a fold far forward, making the head look like a turtle's pointed head protruding from its shell. This frog shows a pattern of yellowish or whitish thread lines, corresponding exactly to the lines along which the skin naturally splits during the moulting. Not only is there the line along the middle of the head and back but there is a similar one along the midline of the ventral surface from the lower jaw to a point of meeting posteriorly with the line of the back. Branches from this main line extend along the middle of the posterior face of the femur to the tibia, along the back edge of the tibia to the heel, over this and out on the foot to a point just above the sole tubercles, where it is lost to the naked eye. There are also two branches opposite each other on the breast; they extend outward and forward to the humerus, thence out along the humerus and lower arm on to the hand. These lines may be obscure or very conspicuous.
The habits and life history of Hypopachus cuneus are not on record.
FAMILY VII. RANIDAE. (Refer to pp. 8, 11 and 48.)
THE COMMON LEOPARD FROG (The Leopard Frog is called "Spring Frog" in Florida and "Grass Frog" in New York.)
Rana pipiens Shreber (Rana pipiens Shreber is Rana virescens Kalm (Cope) and Rana virescens brachycephala Cope ("Batrachia of North America"). It has not been possible, in living material obtained from New England, New York, Michigan, Minnesota, Wisconsin, Colorado, Texas, and Arizona, to make a distinction into these subspecies. The variation of the frogs is remarkable, but no fundamental characteristic (such as proportionate length of head and body, leg measurement, etc.) remains stable when a large series of frogs from adjoining districts are examined. Eastern specimens are likely to be green or brown, Southern and Western specimens are more often grey. Eastern frogs, especially those that frequent the salt marshes of the coast, are more smooth-skinned and slender, and on the whole, more delicately moulded, while Southern and Western specimens are much more robust in build, have a rougher skin, and attain a larger size. The material is very confusing. With a smaller series, the subspecies might have been granted. With a still more complete series, it is possible that two or three intergrading varieties of the species Pipiens could be recognized. Much systematic study of such a series of frogs, combined with knowledge of their habits and life histories, could alone produce any definite conclusion in the matter.)
The Leopard Frog is one of the most beautiful in colouring of all our common frogs. It is better known than others, not only because of its wider distribution and greater numbers, but because it has the habit of going considerable distances from its pond, or marsh. It is the frog met with when we walk across country, through fields and orchards. As we wander slowly through the meadow these frogs leap out from underfoot. They make long, low leaps, seldom appearing above the clovers and grasses. They are not satisfied with one jump for safety, but give three or four in succession, each probably in a somewhat different direction.
If we walk still more slowly and watch very carefully, we are likely to catch a glimpse of a spotted back and of squirted water as an especially large one makes a flying leap. If we try to catch a large one and meet with any success, we discover that this habit of squirting water--as though into the face of an enemy--may sometimes result in protection to the frog, since the water is disagreeable in odour.
Our greatest effort, however, comes in keeping a Leopard Frog, after the chase is over and when we have him in our very grasp. The slippery skin, the slender body, and strong hind legs serve him in just such emergencies. He gives most unexpected and vigorous jerks of the body to free himself. However, if he finds his efforts unavailing, and feels a firm hand about the posterior part of his body and the strong thighs, he stops struggling and begins to expostulate in a very decided but musical voice. We watch and listen in astonishment and admiration. Who knew that a frog could talk in so charming a fashion? Indeed, the sound is so musical, that we might almost say he sings. The vocal pouches swell into rounded projections behind and under the ears; they distend and collapse alternately as the musical notes are uttered.
The vocal pouches are elongated in shape, extending obliquely above the arm. They start from a point somewhat below the jaw in front, and extend upward on the sides of the frog, nearly or quite to the lateral fold. When the pouch collapses, the skin is left wrinkled and baggy in the given region. (Colour Plate XI, male frog.) The glandular band extending backward over the shoulder, marks the margin of a loose, drooping fold of skin. The sound produced is a soft guttural in quality, low-pitched (about E, an octave below E of the first line), and vibrant,