SUB-CLASS II 



DIBRANCHIATA 



51)7 



Distribution world-wide ; most abundant in Europe, Asia, and North America. As 



an index fossil of the Jura and Cretaceous, 



this genus is scarcely less important tlmn h 



Ammonites. 



Sub-Genera : Pachyteutkis, Bayle (Fig. 1241, A). 

 Guard perfectly smooth. Confined to Lower Lias. 

 B. acutus, Mill. 



Megateuthis, Bayle (Dactylotcuthis, Bayle ; 

 Paxillosi), (Fig. 1241, B). Apex of guard with 

 two or three usually short grooves. Middle Lias 

 to Lower Cretaceous. B. paxillosus, B. gigantcus, 

 Schloth. ; B. elongatus, Mill. ; B. subquadratus, 

 Roem., etc. 



JBelemnopsis, Bayle (Hibolithes, Montf. ; Gastro- 

 coeli, Canaliculati, Hastati], (Fig. 1241, D, E). 

 Guard with deep and usually long ventral furrow 

 extending from alveolar margin toward the aju-x, 

 with or without dorso-lateral lines. Middle Jura 

 to Middle Cretaceous. B. canaliculatus, Schloth. ; 

 B. absolutus, Fisch. ; B. unicanaliculatus, Ziet. ; 

 B. minimus, Lister. 



Fio. 1239. 



Belemnites compressus. Lias ; 

 Guiulershofen, Alsace. 

 Phragmocone with well-pre- 

 served conotheca. a, Asymp- 

 totic line ; h, Hyperbolic 

 area ; v, Ventral area. 



Fio. 1240. 



Belemnites (Duvalia) 

 dilatatus, Blv. Neo- 

 coinian; Justithal, 

 Lake of Thun, Switzer- 

 land. 



Fio. 1241. 



A, J5. (Pachyteuthis) acutus, Miller. Lower 

 Lias; Lyme Begis, Dorsetshire. B, B. (Mega- 

 teuthis) pcmllosus, Schloth. Middle Lias ; M.-tzin- 

 gen, Wiirtemberg. C, B. (Pseudobelus) bipartitus, 

 Blv. Lower Cretaceous ; Castellane, Basses 

 Alpes. a, b, c, Dorsal and ventral aspects and 

 cross-section, 1/1- A & (Belemnopsis) <" 

 latus, Schloth. Inferior Oolite; Wurtembcrg. 

 E, B. (Belemnopsis) hastatus, Blv. Oxfordian ; 

 Dives, Calvados. 



Pseudobelus, Montf. (Bipartiti), (Fig. 1241, (7). Guard thin, slender, with deep dorso- 

 lateral grooves, with or without ventral furrows. Upper Lias to Lower Cretaceous. B. exilis, 

 d'Orb. ; B. bipartitus, Blainv. 



Actinocamax, Mill. (Gonioteuthis, Bayle), (Fig. 1242). Guard cylindrical, submucrpnate, 

 with short but very deep ventral furrow ; anterior end foliaceous, and very liable to dissolu- 

 tion. Phragmocone only very slightly inserted in the guard, the two portions usually 

 separated by an interval. Middle and Upper Cretaceous. B. subventricosus, Wahlb. ; B. 

 quadratics, Blainv. 



Belemnitella, d'Orb. (Fig. 1243). Guard cylindrical, with short, deep ventral furrow 

 falling short of alveolar margin. Phragmocone inserted in guard. Vascular impressions 

 often beautifully preserved. Upper Cretaceous. 



