WILLISTON AND CASE: KANSAS MOSASAURS. 



27 



The point of chief interest in this relation is the value that can be 

 given to this character. Is it individual, specific or generic? Marsh 

 has called it generic, but we think ati examination of the two very 

 complete specimens of C. tortor and C. velox in our Museum will con- 

 vince any unprejudiced student that he is in error. 



A comparison of the figures herewith given of the paddles will show 

 their great resemblance, and these two forms of paddles have been 

 figured because the species are the most unlike of any that we know in 

 the genus. As all the small specimens seem to possess this character, 

 and as they cannot be called immature specimens, we believe the 

 character is a specific one. As Marsh says, typically both Clidastes 

 and Edestosaurus have a non-emarginate coracoid, so that neither 

 name could apply to the emarginate form, were it generically distinct. 



Our Museum also contains both forms of the coracoid pertaining to 

 the genus Platecarpus, of which Holosaurns is a synonym. 



While studying the specimen above described, a striking similarity 

 was observed to several other specimens already determined with con- 

 fidence as C. puniilus Marsh. A more careful comparison failed to 

 bring out any real differences beyond size, and even this was shown to 

 be very inconstant. 



The following comparison of the descriptions given by Marsh will 

 be of interest. 



C. piimiliis. 



Teeth. Nearly round at base, 

 somewhat curved and with smooth 

 enamel. 



Quadrate. The rugose knob 

 near the distal end of the quad- 

 rate is similar to that in C. Wy- 

 mani (just below the posterior 

 superior process is a prominent 

 rugose knob with a deep pit un- 

 der it), but has no articular pit 

 under it. The hook is compara- 

 tively short and has a free com- 

 pressed extremity. The articular 

 margin is not deflected toward 

 the meatus. 



Cervical Vertebrae. Artic- 

 ular face nearly vertical, and 

 having a broad transverse outline 

 with faint superior emargination. 

 The hypapophysis stout and trans- 

 versely triangular. 



C. velox. 



Premaxillary and maxillary 

 teeth smooth and subcompressed. 



The great ala less curved than 

 in E. dispar, concave transversely 

 on both surfaces. The alar pro- 

 cess has its articular process very 

 narrow in its extension over the 

 great ala. No notch in posterior 

 margin of external angle. On 

 the ridge below the angle and 

 nearly opposite the meatal pit is 

 a strong rugosity which is rudi- 

 mentary or wanting in C. dispar. 

 The posterior margin of the hook 

 is only a narrow tongue projecting 

 towards the meatal pit, instead of 

 a broad articular surface. 



Articular face transverse. 



