CLASS I.— CEPHALOPODA. 



ObDER I. — DlBEAJs-CHIATA. 



Family III. — Teutihd^. 

 Phyllotetjthis, Meek and Hayden. 



Type, P. subovatus. Cretaceous. Nebraska. 



Fen corneous, thin, subovate, slightly concave below., and 

 convex above. From behind the mid- 

 dle it narrows towards the front, the 

 outline of the lateral margins being 

 convex, while the posterior end is more 

 or less obtusely angular. Apparently 

 related to Beloteuthis and Teudopsis. 

 (Seep. 168.) 



Family IY. — Belemnitid^.* 



The Shell of Belemnites consists 

 fundamentally of: — 



1. A hollow cone, the phragmocone, 

 Fig. 1, p, with a thin shelly wall, 

 termed the conotheca, c, and which is 

 divided by transverse septa, concave ^ 

 above and convex below, into cham- « 

 bers or loculi ; the septa are perforated S 

 near the ventral margin by a siphuncle. S 



2. A guard or rostrum, g, more or o 

 less extensively enveloping the apical 

 part of the jDhragmocone. *' The 

 phragmocone is not a chambered 

 body made to fit into a conical hollow 

 previously formed in the rostrum, 

 as some have conjectured, but both 

 rostrum and cone grew together ; the 

 former was formed on the exterior of 

 a secretive surface, and the latter on 

 the interior of another secretive sur- 

 face." (PhilUps.) 



The rostrum is composed of calca- 

 reous matter arranged in fibres per- 

 pendicularly to the planes of the laminae of growth, 



* See p. 173. 



b2 



Fig. 1. 



Pro- 



