OCR Text |
Show 1891.] RACES OF RANA ESCULENTA. 377 large or small, blunt or compressed. The length indicated in the measurements below is the basal, i. e. taken along the attachment of the tubercle to the foot; the length of the first toe, given for comparison, is taken from the tubercle; and the length of the tubercle is also compared to the length of the c m s or tibia measured in the flesh. 2. The comparative length of the tibia to the thigh ; this is shown by pressing the two close together and maintaining the tibia at right angles to the axis of the body ; the tibial extremity is then found to overlap, to meet or to fail to meet its fellow placed in the same position. Only in form 1 do they overlap 1, and this character alone differentiates it from the three others. 3. The presence or absence of short glandular folds along the back, in addition to the glandular dorso-lateral fold. The presence of these folds differentiates form 4 from the three others. 4. The presence or absence of bright yellow pigment on the lumbar and post-femoral regions. This pigment is constantly absent in form 1, and very seldom in form 2. The character unfortunately cannot be made use of with spirit-specimens. By means of these characters we are able to draw up the following key, which is imperfect only in so far that forms 2 and 3 are not distinguished from each other in an absolute manner; this difficulty, however, cannot be overcome, as the two forms do run completely into one another, aud future investigations may even render their separation unadvisable. No dorsal folds. 'Heels overlapping. 1. ridibunda. Met. tubercle 2^-4> (2. typica. „ 2-3 Heels not, overlapping 3. lessoncs. „ l£-2 £ %-\4\ | ° 7-10 •5 § m a 5-8 S'v, Dorsal folds (4. nigromaculata. „ 1-1U "•£ 5-8 Other characters have been added to complete the definitions. In the following tables a complete list of the specimens in the British M u s e u m is given, together with measurements taken from individuals from various localities. In these measurements the figures in column 1 give the length, in millimetres, from snout to vent; in column 2, the length of the tibia; in column 3, the length of the foot measured from the outer metatarsal tubercle to the end of the fourth toe ; in column 4, the length of the inner toe ; and in column 5, the length of the inner metatarsal tubercle. The specimens enumerated are but a portion of the material studied, a picked series, in which consequently abnormal specimens, i. e. such as fit least well in the technical definitions, are in greater proportion than iu collections made without discrimination. The number of specimens in the M u s e u m is also greater than appears from the figures, as I have abstained from counting in any case 1 As in the various species of the temporaria-groxnp, all of which, however long or short the hind limbs, possess this character. |