180 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 21, 



Caprinula brevis, n. s. Pl. XVII. fig. 1 & 2. 



Shell somewhat inequivalve : both valves slightly curved, short, and 

 increasing very rapidly in diameter, so that the breadth at the junc- 

 ture of the valves is about equal to the length of the longer valve. 

 The junction of the valves is very slightly obUque. 



Surface of one valve smooth, of the other covered with very fine 

 longitudinal flutings ? 



In the hippurite hmestone at Lisbon. 



The largest specimen seen is 4^ inches in diameter. 



The species is not common at Lisbon, and I have only one fragment 

 retaining the outer surface of the shell, which may perhaps belong to 

 another species. C. brevis is readily distinguished from either of the 

 other species by its peculiar proportions. 



Plate XVII. fig. 1. A young specimen nearly perfect. 



Fig. 2. Section of an old specimen. 



Caprinula d'Orbignii, n. s. Pl. XVIII. fig. 1 & 2. 



SubcyHndrical : both valves slightly curved, and set rather ob- 

 liquely together, so as to give the whole shell an irregular sigmoidal 

 flexure. The valves are of very unequal length, but the end of the 

 interior of the longer valve is cut off by septa, so that the cast of that 

 valve is of about the same length as that of the other. 



The exterior of both valves is similarly ornamented with strong 

 uneven flutings which are frequently interrupted by strongly marked 

 lines of growth. 



Common in the hippurite limestone at Lisbon. 



The usual size of this species is about 2 inches in diameter ; but 

 one fragment which I believe to belong to the species is above 4 

 inches in diameter. I have no perfect specimen, but many fragments 

 are between 4 and 6 inches long. 



I could not resist the temptation to name this species after M. 

 Alcide d'Orbigny, to whom this family of shells is especially indebted. 



Plate XVIII. fig. 1, Portion of the exterior of both valves. 



Fig. 2. Cast. 



Caprinula Doublieri, D'Orb. sp. (Post, Pl. XVII. fig. 3 & 4.) 

 Caprinella Boubliei^i, D'Orb. Pal. Fran9. T. Cret. pl. 541. 



Lower valve of two whorls, the inner one increasing rapidly in size, 

 the outer whorl of nearly the same diameter throughout. Upper 

 valve very short and nearly smooth. 



In the hippurite limestone near Lisbon. 



I have seen few specimens of this species, — none with the valves 

 united ; I therefore take the proportions of the two valves from M. 

 D'Orbigny's figure. My largest specimen is 4 inches across. 



The section shows the same lobes of the body and tubes of various 

 sizes down the walls of the shell as in the preceding species, for which 

 reason I place it in Caprinula instead of Caprinella, of which the de- 

 finition is to have all these tubes of the same size. 



Plate XVII. fig. 3 a. Lower valve with the surface destroyed. 



