144 The American Naturalist. [February, 



distinction which is the hnp»rtnnt poi„t. heticeen the parotic process of 

 the e.roenpital and the element irhie/i ronfuins the post, rior semicircular 

 cunn/.r What then is the element which articulates with the quadrate 

 in the different orders of the Keptilia?" 



The sentence quoted from Siebenrock is misleading. Siebenrock 

 dot:-* not distinguish between the parotic process of the exoecipital and the 

 element >rhirh <-ontains -<■ lar canal. He says: not 



on I [i the jntrotie process hut tin irhole portion anterior to the foramen is 

 homologous to the paroccipital. This whole portion, of course, contains 

 also the parotic process. The sentence of Siebenrock translated by- 

 Cope is printed at the end of the paper in a resume. A full account 

 of the conditions is given on p. 209. " Die bisherige Anschauung, 

 daw am Processus paroticus des Pleuroccipitale (exoccipitale) das 

 Upisthotieum zti fimlen sei. ist daher absolut unrichtig, sondern der 

 game rordere Theil des Pleuroeeipitale. u-clche die hintere Partie, des 

 (j f hares enthiilt. sammt dem Processus paroticus ist als das eigentliche 

 Paroccipitale aufzufassen.j Vergleicht man dasselbe mit dem bei den 

 Schildkrdten zeitlebens separirten Paroccipitale, so ergiebt sich schon 

 aus der Lage und Function die Homologie der beiden Knot-hen.'' 

 And later: "Die gleichen Yerhiiltnisse bestehen bei Hatteria, nur 

 bleibt bei dersellben das Paroccipitale viel laenger vom Pleuroccipi- 

 tale (exoccipitale) getrennt, als bei Lacerta." 



That Prof. Cop* has not studied Siebenrock's paper is also evident from 

 the following sentence : " In the Testudinata, and according to Baur, in 

 Sphenodon, the element which extends externally from the exoecipital 

 to the quadrate is continuous with the opisthotic, but the semicircular 

 canal is included in its proximal part only. Here the structure is en- 

 tirely different from that which characterizes the Squamata, where the 

 opisthotic does not extend distal of the canal and fuses early with the 

 exoecipital." It is still more evident from the following words : " In 

 the Squamata, where the opisthotic is restricted to the region of the 

 canal and does not reach the quadrate, thissocalled paroccipital is dis- 

 tinct." Cope thinks the paroccipital -f- otic portion of the paroccipi- 

 tal or opisthotic in the Testudines is not homologue to the paroccipital 

 + otic portion of the paroccipital or opisthotic of the Squamata, and 

 has the idea that this bone, paroccipital. I >wen, opisthotic, Huxley, oc- 

 cipitale externe, Cuvier, consists of two elements, the outer one — the 

 pan-, capital— and the auditory portion, the opisthotic. He admits 

 that '■ the direct evidence for such a primitive division of this element 

 (occipital externe, Cuvier ; paroccipital, Owen ; opisthotic, Huxley) 



