SUBCLASS II 



DIBRANCHIATA 



683 



Fig. 1321. 

 Diploconus belem- 



nitoidea Zittel, 

 thoiiian 



Ti- 



Straraber" 



tion. Phraginacone only very slightly inserted in the guard, the two portioiis usually 

 separated by an mterval. Middle and Upper Cretaceous. B. suhvcntricosus Wahlb. ; B. 

 quadratus lilainv. 



BelemnitcUa d'Orb. (Fig. 

 1320). Guard cylindrical, with 

 sliort, deep ventral furroAV fall- 

 ing short of the alveolar margin, 

 Pliragniacone inserted in guard. 

 Vascular impressions often 

 beautifully preserved. Upper 

 Cretaceous. 



Diploconus Zitt. (Fig. 

 1321). Guard short, obtusely^ 

 conical, and liaving a coii- 

 centric lamellar structure, not 

 radial and fibrous. Phragma- 

 cone reaching nearly to the 

 posterior end of the giiaid. 

 Tithonian. 



Bayanoteuthis Mun.- 

 Chalm. Guard long, cylind- 

 rical, mucronate, with shallow 

 lateral grooves. Dorsal area 

 rougheried. Pliragmacone very 

 slender and long, oval in 

 section. Eocene ; Paris Basin 

 and Ronca, Italy. B. rugifer 

 Schloenb. 



Vasseuria Mun. - Chalm. 

 Guard slender, elongated- 

 conical, with a nuniber of 

 longitudinal grooves extending 



from the apex. Pliragmacone more than one-half as long as the guard. Septa 

 oblique, their necks extending from one septum to the next. Very rare in the Eocene 

 of Brittany. 



Belemnosis Milne Edw. Very rare in the English Eocene. Styracoteuthis Crick. 

 Intermediate between Belemnitella and Bayanoteuthis. Eocene ; Arabia. 



Beloptera Blainv. (Fig. 1322). Guard short and somewhat s wollen at its forwaixi 

 end, which makes a slight angle with the pliragmacone ; on either side it is expanded 

 into a conical projection. Eocene. 



Belopterina Mun.-Chalm. Like Beloptera, but without the lateral wing-like 

 expansions. Eocene. 



Fig. 1320. 



Belemnitcs (Belemnitella) mucronatus 

 Schloth. Upper Cretaceous ; Drenstein- 

 furth, Westphalia. A, B, C, Ventral, dorsal 

 and lateral aspects. 2/3, 



Fig. 1322. 



Beloptera belem- 

 nitoidea Blv. Calcaire 

 Grossier ; Paris Basin. 

 Ventral aspect. 



Family 2. Belemnoteuthidae Zittel. 



Shell composed of a conical phragmocone and proostracum, the guard being reduced 

 to a thin calcareous or horny Investment of the phragmacone. Ten arms of nearly equal 

 length, each heset with a double row of hooJcs. Ink-sac present. Trias and Jura. 



Acanthoteuthis Wagner and Münst. {Belemnites Quenst. p.p. ; Ostracoteiithis Zitt.) 

 (Figs. 1323-1325). Phragmacone with numerous septa, and siphuncle having short 

 siphonal funnels ; enveloped externally in a thin granulär calcareous layer represent- 

 ing the guard. Surface of proostracum divisible into a broad dorsal, and two narrow 

 lateral areas which are longitudinally striated and taper toward the front. Dorsal 

 area ornamented witli fine parabolic and also straight longitudinal liiies ; anterior 



