MANUAL OF THE MOLLUSCA. 



Bensselceria, if not synonymoTis with, is closely related to, 

 Meganferis. 



Fossil, 11 species. Silurian to Devonian. Europe, North 

 America. 



CENTEoasTELLA, Billings, 1859. 



Etymology, diminutive of hentron, a spur. 



Type, Ehynclionella glans-fagea, Hall. 



SheJl having the general form of Terehrafula. Dorsal valve 

 with a loop consisting of two riband-lilie lamellae, which were 

 united at an acute angle at the point of greatest extension, 

 whence they recurve in a thin vertical plate which is not 

 attached at either margin, approaching in some respects to 

 Waldheimia. 



Distribution, 4 species. Devonian. North America. 



Leptoccelia, Hall, 1859. (Ccelospira, Hall). 



Appears to differ from Centronella only in consisting of 

 species which have the surface ribbed instead of smooth. 



Distribution, 9 species. Mid. Silurian — Devonian. Europe, 

 North America. No true Terebratulse have been found in 

 beds older than the Devonian. 



Eamllt II. — SpiErFEnrDiE.* 

 SYHiNGOTHYPas, Winchell, 1863. 



Fig. 19. Section throiiDh the beak of the ventral valve of S. typa (Winchell). 

 I, dental plates or lamellae ; t, tube incoraplete ; r, mesial ridge. 



Examples, S. typa, Winchell, Fig. 19; Spirifera distans, Sow. 



Shell like that of Spirifera, with an elongated hinge-line. 

 Ventral valve with a broad mesial sinus, a very broad area, and 

 a narrow triangular fissure closed towards the apex by an 

 external convex pseudo-deltidium ; beneath which, and diverg- 

 ing from it, is another transverse plate connecting the vertical 

 dental lamellae, which are incurved so as to nearly join their 

 inferior edges, thus forming a fissured tuhe, which projects 

 beyond the limits of the plate from which it originates into the 

 interior of the shell. A low median ridge extends from the 



See p. 271. 

 54 



