SCALPELLUM. 21 



flat ; internally convex. The umbonal, freely projecting portion is sometimes more than 

 half, sometimes only about one third, of the entire length of the valve. This portion curls 

 outwards and likewise upwards. The degree of curvature and the width {in and n), in pro- 

 portion to the length, varies. The upper and lower margins are approximately parallel to 

 each other ; the umbonal end of the growing surface is bluntly pointed. This valve differs 

 from its homologue in S. vulc/are, in being larger, much narrower in proportion to its length, 

 more massive, and with a far larger portion of the umbonal end freely projecting ; also in 

 the approximate parallelism of the upper and lower margins, and in the umbonal end of the 

 growing surface being pointed instead of square. In 8. vulgare the upper margin is much 

 more curled upwards than the lower, and the freely projecting portion is only one fifth of 

 the entire length of the valve. 



Taking the largest specimens in Mr. Wood's collection, the freely projecting portions 

 of the carinal latera must have stuck out like horns, curling from each other and a 

 little upwards, for a length of a quarter of an inch. So again, the much flattened horns of 

 the rostral latera, curving from each other, but not upwards, must have projected half an 

 inch beyond the probably rudimentary rostrum. The capitulum must have presented a 

 singular appearance, represented in the imaginary restored figure (fig. 1 «), with its pair of 

 projecting horns at both ends. 



Peduncle ; calcareous scales unknown, but undoubtedly they existed. 



Varieties : the variation in the rostral and carinal latera has already been pointed out. 

 In Mr. Wood's collection there are numerous scuta, terga, carinas, and carinal latera, 

 from Sutton ; and these are all smaller than those above described, which come from 

 Sudbom-ne, and than some others in Sir C. Lyell's collection from Gedgrave. All these 

 places, however, belong (as I am informed by Mr. Wood) to the same stage of the Coralline 

 Crag. In the Sutton specimens the carinal latera show the same character as in those from 

 Sudbourne, but the carina apparently is not internally so much narrowed in under the 

 umbo ; this, however, is a character which is conspicuous only in the larger Sudbourne 

 specimens, and anyhow cannot be considered as sufficient to be specific. 



I may take this opportunity of stating, that in Mr. Harris's collection of organic remains 

 from the chalk detritus, at Charing, in Kent, I have found the upper part of a carina of 

 a very young and minute Scalpellum, which cannot be distinguished from this species; 

 but considering the state of the specimen, it would be extremely rash to believe in their 

 identity. All the known cretaceous species have the umbo at the apex, so that the Charing 

 specimen differs remarkably from its cretaceous congeners. 



