THE AMERICAN NATURALIST [Vol. XLIII 



(mi the other hand, obtained excellent results, and his descriptions 

 of the vertebrae of the various forms will be of great service to 

 the student even though his conclusions are not accepted. 



A new family "Ophiderpetontidae" is proposed to include 

 the genera Ophiderpeton and Thyrsidium, the former of which 

 was included in Lydekker's Dolichosomatidae. The family 

 characters are solely those exhibited by the ribs and vertebrae. 

 Under the heading of Ophiderpeton the author rediscusses the 

 question of the "Kammplatten" and dismisses the subject with 

 the remark "dass sie nichts mit den Stegocephalen zu tun 

 haben. " Herein he has committed an error, for Fritsch has 

 distinctly figured 2 a nearly complete specimen of Opliuh -rpcton 

 j>< rsuful, us Fr. with the •Kammplatten" in place near the 

 cloacal region of the animal. The whole question of the 

 "Kammplatten" has recently" been reviewed by the present 

 writer. There is a great deal of uncertainty as to what the 

 true nature of the "Kammplatten" really is. That they do 

 occur in selachians as stated by Fritsch 4 does not at all imply 

 that they may not also occur in Ophiderpeton, and they cer- 

 tainly do occur here if Fritsch has correctly interpreted his 

 specimen. 



Schwarz adopts the two suborders Aistopoda and Microsauria 

 for the " Holospondylen Stegocephalen," but does not seem to 

 understand the differences which exist between these two sub- 

 orders, and especially is this true when he includes the Ptyoniidae 

 in the Mi.-rosauria, since Ptyonius and its allies are typical 

 members of the group Aistopoda. There is really but little 

 difference between the groups Aistopoda and the Microsauria 

 structurally, and, as Schwarz suggests, they undoubtedly arose 

 from the same stem much as did the lizards and snakes, but 

 they are just as distinctly members of different groups as are 

 the Lacertilia and Ophidia. Xo form is more typically an 

 aistopod than the Ptyonius. The subordinal characters are 

 found in the vertebrae, in the lack of limbs, the elongation of the 

 body and especially in the attenuation of the skull with its con- 

 comitant structural differences. 



The final conclusion attained by the author is that, with 

 Jaekel, he would divide the Stegoeephala into two groups, the 



-Frits,!.. 1901. "Fauna der Gaskohle," Supplement, Vol. IV, p. 89. 

 Biol. Bulletin, "Vol. XIV, No. 4, 1908. 



