CLASS I.'-0EPHAL0P013A. 



OeDEE, I. — DlBBANCHIATA. 



Family III. — Teuthid^. 

 Phyllotettthis, Meek and Hayden. 



Type, P. subovatus. Cretaceous. Nebraska. 



Pen corneons, tbin, snbovate, sligbtly concave below, and 

 convex above. Prom 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. 

 (See p. 168.) 



Family IY. — Belemnitid^.* \i\isssM8sxx >.!^^ 



The Shell of Belemnites consists 

 fandamentally 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 

 near the ventral margin by a siphunde. 



2. A guard or rostrum, g, more or 

 less extensively enveloping the apical 

 part of the phragmocone. " 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." (PhiUips.) 



The rostrum is composed of calca- Fig. i. 



reous matter arranged in fibres per- 

 pendicularly to the planes of the laminse of growth. Pro- 



* See p. 173. 



b2 3 



