258 BALANIDJE. 



unusually close to the outer lamina. In very young specimens the 

 inner lamina of the parietes is ribbed, in lines corresponding with the 

 longitudinal septa, as is the case with most species of the genus; but 

 in medium and large-sized specimens, there are between the ribs, thus 

 produced, from one to four smaller ribs, which do not correspond with 

 any longitudinal septa ; they are finely denticulated at their bases, and 

 may be considered as the representatives of longitudinal septa which 

 have not been developed and reached the outer lamina. I have seen 

 no other instance of this structure, namely, the presence of a greater 

 number of ribs, on the inner lamina of the walls, than there are longi- 

 tudinal septa. The radii have their summits generally parallel to the 

 surface of attachment, as is usual in the first section of the genus, but 

 sometimes they are slightly oblique : the septa sometimes rudely branch 

 a little, but they exhibit scarcely a trace of denticuli : the interspaces 

 are filled up quite solidly. The alee have their summits very oblique ; 

 their Bntural ed°;es are finely crenated. 



Basis, rather thin, translucent, not permeated by pores ; obscurely 

 furrowed in lines radiating from the centre : the circumference is 

 marked in a peculiar manner by the longitudinal septa, and by the 

 tips of those intermediate, denticulated ribs, which occur on the inner 

 lamina of the parietes. 



Mouth : labrum with six teeth : mandibles with the fourth and fifth 

 teeth small and rudimentary : maxillae, with a small notch under the 

 upper pair of spines; in the lower part there is a single large spine. 

 Cirri, dark brownish purple, making a singular contrast with the white 

 operculum and shell; first pair, with one ramus, having twenty-six 

 segments, and about twice as long as the shorter ramus, having twelve 

 or thirteen segments, with their front surfaces protuberant. In the 

 second pair the segments are but little protuberant: third pair about 

 one third longer than the second pair : sixth pair, elongated, having in 

 the same individual forty-six segments ; these segments have shield- 

 shaped fronts, bearing five pairs of spines, with some minute interme- 

 diate bristles. There is the usual point at the dorsal base of the penis. 

 Range : Geological History. — This species is common on the shores 

 of Scotland and Ireland ; the most southern point of Europe whence 

 I have happened to see a specimen is Tenby, in South Wales : but I 

 have no doubt it is found further south ; and Mr. Jeffreys, who knows 

 this species well, has found it common on the extreme southern 

 shores of England. In the United States, it is found on the shores of 

 Maine and Massachusetts : northward, I have seen specimens from 

 Iceland, from Davis's Straits, and from Lancaster Sound, in lat. 74° 

 48' north ; these latter I owe to Sir J. Richardson. It is an inhabitant 

 of deep water ; in Mr. Thompson's collection there are several specimens 

 from the Bay of Belfast, marked twenty-five fathoms, and one group said 

 to have come from " about fifty fathoms, on the coast of Antrim :" one 

 specimen from Cape St. Anne, Massachusetts, is marked as having come 

 from only five fathoms. This species is commonly associated, on both 

 sides of the Atlantic, with B. crenatus, and sometimes with B. Hameri 

 and Verruca Strumia : mollusca, such as pectens, modioli, and oysters, 

 offer the most usual surfaces of attachment : I have, however, seen many 



