62 G. F. MATTHEW: ILLUSTEATIONS OF 



limbo less thau one third from the front of the valve. Tumid part of the valve orcupying 

 about one third of its length and about one half of its width ; valve flattened toward the 

 anterior and posterior ends. A faint narrow rim is traceable around the outer edge of the 

 valves. 



The cast of the right valve has a triangular umbonal prominence, about one third from 

 the front ; the prominence is limited in front by a sharp and deep furrow, placed at right 

 angles to the hinge line, and extending thence toward the base of the valve ; the umbonal 

 elevation is somewhat hollow in the middle, where it bears a sharp narrow ridge, which 

 is directed toward the posterior margin, at an angle of 50' from the hinge line ; a faint 

 furrow connects this ridge with the point of the umbo. 



The outer surface of the valves of this species is marked by numerous concentric 

 strise, and by two faint radiating furrows, extending on each side of the tumid part of the 

 valve to the basal margin. 



The sharp median ridge and connected furrow, seen in the cast of the right valve of 

 this species, are similar to those on the dorsal valves of some Brachiopods, but the i^osition 

 of the iimbo separates it from that class of molluscs. 



Length, 1 mm. Width, | mm. 



Horizon and Locality. In the fine, grey shales of Div. l.c, at Hauford Brook, St. Mar- 

 tin's. Infrequent. 



Lepiditta curta, n. sp. (Plate VI. Fig. IT.) 



Obliquely semi-elliptical and about two sevenths longer than wide ; hinge-line nearly 

 straight ; timbo depressed, less one quarter from the front of the valve. Valves flattened 

 toward the base and posterior end, the anterior and posterior margins have a flattened, 

 depressed rim ; and the front of the rim in the two valves was apparently connected by a 

 triangular piece not bounded by distinct sutures. 



The interior of this shell has roughened zones or undulations concentric to the umbo. 



This organism is not unlike the crustaceans of the genus Estheria, but its resemblance 

 to the preceding species, in form and hinge-characters, indicates a generic relation. 



Length, 1^ mm. Width, 1\ mm. 



Horizon and Locality. In the fine dark shales of Div. l.d, at Porter's Brook, St. Mar- 

 tin's. Rare. 



LEPIDILLA, n. gen. 



This peculiar little organism may be described as follows : — Bivalve (?) shell having 

 the hinge and body of the valve, or plate, in different planes. Hinge line straight, project- 

 ing from the general contour of the shell ; ximbo and hinge line separated from the body 

 of the valve by a sinus or emargination, behind which there is a foramen. 



Lepidilla anomala, n. sp. (Plate VI. Pigs. 18, 18a. b. and c.) 



General outline of the valve, or plate, nearly circular ; outline broken by the project- 

 ing umbo and the notch in front of it ; a narrow, raised margin goes round the edge of the 

 valve, except at the anterior end. 



