199 



LlNGULEPIS ROTUNDA, n. Sp. PI. XIV, figs. 4 a-f. 



Minute, valves tumid ; the ventral ovate-acuminate, the dorsal nearly Lingnlepis 

 orbicular. 



Ventral valve rather bluntly pointed, and marked by undulating ridges 

 of growth, irregularly spaced. Interior. The hinge area is high and has 

 a distinct pedicle groove, narrow deltidium and wide marginal area. The 

 visceral callus extends half way of the length of the valve, and here the 

 central group of muscles are placed. Divergent ridges on each side of 

 the visceral cavity indicate the position of the lateral scars ; and from 

 these ridges extend forward, arching toward the front of the valve, faint 

 impressions of the vascular trunks. The margin of the valve is flattened 

 at the sides and in front. 



The dorsal valve is nearly circular in outline and strongly arched ; the 

 slope is most abrupt toward the lateral margins, and the valve is somewhat 

 flattened on the front slope. Interior. No hinge area is apparent on this 

 valve which is almost vertical at the cardinal line. Two small pits near 

 the hinge are in the position of the lateral muscles ; from here a broad 

 medium septum extends nearly to the anterior third of the valve ; on 

 each side of this ridge are prints of the central muscles and at its extre- 

 mity those of the anterior laterals. Lateral ridges more widely set, and 

 less divergent than those of the ventral, separate the scars of the lateral 

 muscles from the visceral cavity. In front of the lateral ridges are faint 

 impressions of vascular trunks, that go somewhat directly toward the 

 front margin. The edges of the valve at the sides and front are flattened. 



Sculpture. The outer surface of the ventral valve shows traces of 

 growth ridges, but nothing of this sort was observed on the dorsal, which 

 is covered with a minute tuberculation. 



e, Length of the ventral, 4 mm.; width, 3 mm. The dorsal is 1 

 mm. shorter than the ventral. 



Horizon and locality. In gray flags of the middle division (Div. C, 2 c) Resembles O. 

 on the eastern slope of the valley of McNeil brook (on the road to Trout 

 brook) Mira river, Cape Breton, N.S. 



This species appears to be near 0. (L.) rotundatus, Wale.* but differs 

 in its longer ventral valve and in the extremely narrow cardinal area to 

 the dorsal valve. 



*U. S. Nat. Mus. Proc. vol. xxi, p. 415, 



