132 



LINGULEPIS ROBERTI PI. VIII., Figs. 5 a and b. 



The following species was described with Lingulella Selwyni in Trans. 

 Roy. Soc. Can., 2nd Ser., vol. I, sec. iv, p. 256 : 



"LiNGOLELLA RoBEETi, n. sp., PI. I., Figs. 2 a and b. 



Lingulepis " Broadly ovate, the ventral value acuminate, having a low mesian ridge 



described. * n * ne posterior third, and slightly upturned at the beak. The dorsal 

 valve tumid posteriorly, with a narrow hinge-margin, the valve has a 

 mesian groove in the posterior quarter, and is flattened toward the front. 

 In the ventral valve the inner surface of the thickened posterior part 

 of the valve carries two pairs of diverging ridges, the inner pair termi- 

 nating at the scars of the anterior adductors, of the outer pair about equal 

 length, but continuous with impressions of the curving vascular trunks. 



The dorsal valve also has in its interior four diverging lidges ; within 

 the two outer ones at the back of the shell is the impression of the pos- 

 terior adductor muscle ; and within the two inner ones, one-third from 

 their ends, are the oval pits of the anterior adductors ; between these 

 scars, and extending backward in the valve, is a faintly marked mesian 

 ridge, placed about one-third from the posterior end of the valve. The 

 pits of the anterior adductors diverge somewhat at their anterior ends, 

 and a short distance in front of them are two small, round pits, near 

 together, which mark the points of attachment of the anterior adjusters. 



Sculpture. This consists of irregular concentric striae which inoscu- 

 late with one another, producing a surface of broken ridgelets, similar to 

 that of an Acrothele ; the concentric ridges are of unequal size, and there 

 are occasional more distinctly marked growth-lines. 



Size. Length of the dorsal valve, 13 mm.; width about the same ; 

 the ventral valve is about 1 '5 mm. longer. 



Locality. Same as Lingulella Selwyni. Found in a sandy limestone 

 of Assise E. 2 (a ? ) by Messrs. Weston and Robert. 



This species is very little larger than Lingulella Seltvyni, but is dis- 

 tinguished by its radular ornamentation and thicker valves ; also by its 

 acuminate upturned beak, its tumid dorsal valve, and by the position of 

 the central muscular scars of this valve ; these scars are in the posterior 

 half of the valve, but in L. Selwyni about the middle of the valve." 



This species approaches Lingulepis in the form of the beak of the 

 ventral valve, and in the advanced position of the lateral muscles, as in- 

 dicated by the lateral septa. 





