462 MESOZOIC TIME. 



terior space. The other genera have a similar anomalous character, 

 but differ in the interior. Fig. 863 represents the lid or upper valve 

 of a Radiolites, showing the projections below (b, c), to which the 

 muscles closing the lid are attached ; and Fig. 864 is the same in 

 Sphcerulites. The Rudistes are supposed to be related to Ghama 

 among the Dimyary Mollusks. 



Some of the Gasteropods are represented in Figs. 838 to 843. Fig. 

 842 is a Nerincea, a shell having a ribbed interior, as shown on page 

 439. The genus began in the Jurassic, and ends with the Cretaceous. 



Of Cephalopods, there were numerous Belemnites (Fig. 844) and 

 Ammonites (Fig. 845). One of the most common of the New Jersey 

 Belemnites is represented in Fig. 844. Some of the Ammonites from 



Fisr. 844. 



Cephalopod. — Belenmitella mucronata. 



beyond the Mississippi are over three feet in diameter. There was 

 also a multiplication of other genera of the Ammonite family, the 

 shells of which are like Ammonites more or less uncoiled ; as Scaphites 

 (Figs. 846, 847), from scapha, a boat; Crioceras, p. 473, from /cpios, a 

 ram's horn : Ancyloceras, from ayKvXrj, a hook or handle ; Hamites, from 

 hamus, a hook ; Toxoceras, from to£ov, a bow; Bacidites (Fig. 848), 

 from baculum, a walking-stick. Turrilites (Fig. 871), a form unlike other 

 Ammonitids in being a turreted spiral ; another, opened spiral, called 

 Helicoceras. Figures of several of these forms are given on p. 473. 

 Among these genera, Ammonites, Scaphites, Ancyloceras, Hamites, 

 Ptychoceras, Bacidites, Turrilites, and Helicoceras have been found in 

 American Cretaceous rocks. Bacidites ovatus (Fig. 848) attained a 

 length of a foot or more, and a diameter of two and a half inches ; and 

 Scaphites Gonradi (Fig. 846), a length of six inches. 



Among Vertebrates, there was the first appearance of several prom- 

 inent modern groups, marking grand steps of progress in the life of 

 the world. 



Among Fishes, Sharks and Ganoids continued to be common, as 

 before. In addition, there were large numbers of the Common or Os- 

 seous fishes, or Teliosts, the tribe which includes the larger part of 

 modern fishes and nearly all edible species. The Cestraciont Sharks 

 still continue ; and the bony pavement pieces of the mouth are not 

 rare fossils. Two views of one from New Jersey are given in Figs. 

 853, 853 a. The Sharks were largely of the modern type of Squalo- 



