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Show 854 APPENDIX C- REPTILES. A MONOGRAPHIC ESSAY QN THE GElfrU^ PHRYNOSOMA. BT CHARLES GIRARD. ; TfiB numerous specimens of nearly all the known species of this genus which are now preserved in the Smithsonian Institution, together with those at the Academy of Natural Sciences - of Philadelphia, have enabled us carefully to study and compare the different members of that most remarkable group, the result of which we propose here to present. Indeed, there are no genera in the saurian order that can so readily be distinguished as that of Plirynosoma. , The body more or less circular in shape, always depressed, sometimes flattened, scattered all over with irregular and spine- like scales; the solid and sttbtriangular h& d provided with acute spines or tuberculous tnobs, the short and conical tail covered with scales similar to those of the body/ sometimes even more prominent, are as many conspicuous features, which must strike any one at the very first glance. Their general aspect, perhaps their sluggishness, may recaH to mind a frog or a toad: hence the vulgar name of horned toads or frogs.' But- the naturalist, with no hesitation, recognises in them true saurians, inasmuch as the body, instead of being smooth, like that of either toads and" frogs, is covered, as just stated, with pc& les of a peculiar character. Besides the spines of the head, the tail, although phort, is another feature by which they disagree from both toads and frogs. So much When these animals aye at rest: as soon as they move, the observer cannot fail to be struck with the fact that phrynosomas never jump or leap, as is the case with the batrachians, to which they have been compared. ~ If we look now more closely at the zoological peculiarities proper to the genus Phrynotoma we will jaee that the vertex is a prominent feature of the head, subtriangularor cordiform, with a sharp . and projecting margin, forming a carina which overlaps the orbits; sometimes it is terminated posteriorly by two spines, one on eaeh side. The occipital region generally presents the largest spines in those species in which these exist as a prominent feature. The, |