^ 



attB an llje |JritisIj |«rassk 



Part II. ^ 



By J. W. D. MARSHALL. 



TEREBRATULA, Klein, 1753. 

 Etjm. — Diminutive of terehratus^ perforated. 



ANIMAL fixed by means of a peduncle passing through 

 an ovate or circular foramen, situated at or near the 

 extremity of the beak of the ventral valve ; foramen partly 

 or entirely margined by one or two triangular plates con- 

 stituting the deltidium. Valves articulated. Labial ap- 

 pendages supported by the crura or basal portion of the 

 calcareous loop. The loop is very simple in design, short, 

 and is attached to the hinge-plate of the dorsal valve in the 

 posterior portion of the shell. There is no median septum 

 as in Waldheimia of King. The shell structure is always 

 punctated. 



It is veiy difficult in a few words to accurately describe 

 the shape of the shell, there being so much variation in the 

 different species ; some are almost spherical, others more or 

 less ovate, transverse or elongated. 



1 The *First Part was published in Vol. YIIL, Part 1 (1895-1896). 



232 



