246 SCALPELLUM ORNATUM, 



Carina! Latera : these appear as if formed of two 

 valves united together ; the upper portion, widening as it 

 ascends in a curved line, terminates in a rounded margin, 

 which enters the deep notch in the upper latera ; the 

 other and lower portion is shorter, and terminates in a 

 square margin abutting against the infra-median latera ; 

 the umbones of the carinal latera project beyond the line 

 of the carina. 



Direction of the Lines of Growth in the Valves. — This 

 should always be carefully observed, on account of the 

 great diversity there is in this respect between the different 

 species, especially when the recent are compared with the 

 older fossil species ; moreover one of the chief characters 

 between the genus Scalpellum and Pollicipes, depends on 

 the direction of the lines of growth. In the scuta, terga, 

 rostrum, and upper latera of the present species, the chief 

 growth is downwards; in the carina, in mature specimens, 

 it is both upwards and downwards; in the carinal latera, 

 both upwards and towards the infra-median latera ; in the 

 infra-median latera chiefly upwards ; and, lastly, in the 

 rostral latera, towards the infra- median latera. 



Peduncle, short, not half as long as the capitulum ; 

 calcareous scales imbricated as usual, tinged red, almost 

 crescent-shaped, acuminated at both ends, of remarkable 

 length, so that in each whorl there are only four scales : 

 a full-sized scale equals in length one of the rostral latera. 

 The tips of two scales, in one whorl, lie under the middle 

 points of the carina and rostrum ; and in the whorl, both 

 above and below, a single much curved scale occupies 

 this same medial position. The peduncle does not seem 

 to have been attached in any definite position to the horny 

 coralline, as is the case with S. vulgare. 



Length of capitulum in the largest specimen *2 of an 

 inch. 



The Mouth is directed towards the ventral surface of the 

 thorax. The Labrum is far removed from the adductor 

 muscle, with the upper part forming an overhanging pro- 

 jection ; I believe there are some very minute bead-like 



