THE DEVELOPMENT OF SCAPHITES 649 



Sonneratia and Desmoceras both change very materially in the ephebic 

 stages, becoming very much flattened through an unusual increase 

 in the height of the whorl. It is found, too, that the same style of 

 suture is characteristic of both Scaphites and of the Stephanoceratidce. 

 This can be seen by looking through Sarasin's 1 paper. It is to be 

 noticed, too, that some species of Desmoceras have a greater number 

 of lobes than other species, and more than are found in Scaphites. 

 In one specimen of Scaphites nodosus quadrangular is the writer found 

 one stage, diameter 8 mm , that resembled the adult of Pachydiscus 

 peramplus Mantell, from the Lower Chalk of England. This is 

 interpreted as being a reminiscence of characters belonging to some 

 ancestor of both Pachydiscus and Scaphites. This was seen in no 

 other specimen of any of the varieties. The sutures of neither form 

 could be obtained for study, as the specimen of the Scaphites did not 

 show it, and the original drawings of this species of Pachydiscus were 

 not available. 



Pachydiscus wittekindi Schliiter, from the Upper Chalk, also is 

 not greatly unlike some of the early stages of Scaphites. Likewise 

 there are reminiscences of Macrocephalites. These may be very 

 superficial resemblances, but they are certainly suggestive. 



Scaphites inermis and S. condoni 



Ontogeny. — These two very small species from the Cretaceous of 

 Oregon and California are both figured in Mr. F. M. Anderson's 

 Cretaceous Deposits of the Pacific Coast, already cited above. Their 

 young stages are so nearly alike, up to the very last whorl, that where 

 a number of the two species are thrown into a vial together, it is 

 almost impossible to separate the two. Numbers 10 and n, Fig. 2, 

 shows the remarkable similarity of the two. 



It was extremely difficult to get drawings with the camera lucida 

 of the sutures of most of these specimens, for they are for the most 

 part only casts, and the sutures do not show. The protoconch is 

 not so rounded in these smaller species as in the interior forms, but 

 otherwise is very little different. The caeca! bulb was seen in one 

 ■case only, and that was not perfectly shown (Number 4, Fig. 2). At 



1 Ch. Sarasin, " Quelques considerations sur les Genres, Hoplites, Sonneratia, 

 Desmoceras, et Puzosia," extract from the Bulletin de la Socicte Geologique de la France, 

 .3d series, Vol. XXV (1897). 



