300 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



will find the zygosphene distinctly represented on figs. 5 a and 5 h, pi. 

 sviii ; figs. 3 b,'3 d,Qb,6 c, pi. xix ; fig. 15 d, pi. xxi ; figs. 3 c and 3 d, pi. 

 xxiii ; fig. 4, pi. xxiv ; and the zygantrum in nearly as many figures. 

 He will also find them well represented in the figures of vertebrte of 

 Clidasies on plates v and xii of the Extinct Batrachia and Eeptilia of 

 North America. In order to substantiate his position, he copies from 

 my work a figure of a vertebra of Clidastes stenojps from which the zygo- 

 sphene has been accidentally broken away. 



Professor Owen places me in the attitude of committing error in ques- 

 tions of fact in regard to the limb-bones and their arches in the Lacertilia 

 and Ojpliidia. My statement is, — " As there are many Lacertilia without 

 limbs, and some serpents with them, their presence in this order is irre- 

 levant in this connection, especially as the arches supporting them are 

 most like those of tortoises and Plesiosaurs." Professor Owen then 

 proceeds to state that there are only twenty-three genera of Lacertilia 

 with reduced limbs, and "extremely few" where they may be considered 

 to be rudiments. Professor Owen can hardly have had in mind the 

 developments of herpetology during the last five or ten years in mak- 

 ing this assertion ; for the genera of lizards now known in which the 

 limbs are rudimental may safely be said to be numerous, and those with- 

 out even rudiments are not a few. Professor Owen appears to have 

 overlooked the entire suborder of the Am;pliishccnia, which are all limb- 

 less with the exception of one genus. He then criticises my reference to 

 serpents with limbs, and observes: — "In certain Oj)liidia dissection has 

 revealed a small styliform bone on each side the cloaca; in a few it is 

 tipped with horn in the shape of a claw. . . . Whether these ap- 

 pendages to the generative parts be homologous with the ' claspers' 

 of sharks or with the ventral fins, and, if the latter, with the hind limbs 

 of lizards, is yet an open question." Eeference to the numerous genera 

 and species of serpents which possess rudimental hind limbs, as well 

 as to the two suborders which possess a pelvis, is here entirely 

 omitted, and the demonstration of the homology of the anal claws 

 above mentioned with true hind limbs appears to be unknown to Pro- 

 fessor Owen. Besides the Boidw, Fythonidw, and Xenopeltidw known to 

 Professor Owen as possessing these rudimental limbs, there are the Li- 

 cJianuridw, Tortricidw, and Stenostomidm ; while the Typhlopidw and Ste- 

 nostomidcc possess a pelvis — the latter family with ilium, ischium, and 

 pubis, as ascertained by Peters. This pelvis is more complete than that 

 of various Lacertilian genera of the Liploglossa group, or of the suborder 

 of the AmpMshcEYiia, which consists, according to Stannius, of a rudi- 

 mental ilium only. My statements on this point are borne out by the 

 facts. My assertion as to the resemblance of the scapular and pelvic 

 arches to' those of tortoises and Plesiosaurs is true in view of the fact 

 that the former has no inferior connection with a sternum, so far as 

 known, an element absent in the orders named and the Ophidia, but 

 present in the lizards, although not universally so. 



