expressed the opinion llmf ibc fore-limbs of the Pylhonomorpha were natatory. 

 Thai tliis view wiis correct I provful by study of the skoh'toii of Clulastes pw- 

 python; and it now appears that the tore-limbs of the latter wert; the (irst 

 ever described. 



The hnmenis of the Mississippi Protostega (see Lcidy, /. c, I'l. viii, 

 Figs. 1-2) is more elongate than that of tlie P. gigas, is less contracted 

 medially, and the (great trochanter or) deltoid crest is longer and stouter. 

 This I called Protostega tuberosa} (Proceedings of the American Philo- 

 sophical Society for 1872, p. 433.) I also pointed out the existence of a 

 third species, as distinguished by the form of the humerus, in the green- 

 sand of New Jersey, which had been referred by Leidy to the "great 

 Mosasnurys^ From this specimen, Leidy inferred the natatory character 

 of the limbs of Mosasaurus. The New Jersey species I called Protostega 

 neptun'ia. A name had l)een already proposed for it; i)ut, as it was unac- 

 companied with specific or generic description, I did not adopt it. This was 

 d(me in accordance with the well-known rule that such names without descrip- 

 tion are useless in nomenclature; and I conceive it to be not only a privilege 

 but a duty to ignore names put forward in this manner. 



The custom of giving generic and specific names without corresponding 

 diagnosis has only recently been introduced, and has no claims to respect. It 

 will, if continued, render the science of paleontology .accessible only to a i)riv- 

 ileged class, who may have control of museums, or who can adopt' a nomadic 

 lite in traveling from one museni to another. In the case of I lie V rotoMega nvp- 

 luiiia^ had Professor Leidy, who figured and described the specimen for th(! 

 lirst time, adopted tiie name already given, 1 should have WM bound lo em- 

 ploy tlie latter, ascriljing it to Leidy as tlie author; but, as he lefl il among liu; 

 synonymy of the Mosasauroids, I hav(^ thought il aiUisalile to follow Inni. 



PYTHONOMORrHA. 



TIh' characters which distinguish this order are the following: 

 1. The (|iiadrate bone is attarlK^d to the cranium by a giniflymoid articu- 

 lation, admitting oi' free movement. 



^1. The ribs an; attached by simple articulations lo sini,de arlicular i'acets 

 oi ditipuphyses springing from the bodies of the vertebra;. 



' I iiuiilvcrtciitlv wrote I'Uitenirpni tiihiroKiin in tlii' abovi^ essay. 

 If) V 



