22 FOSSIL CIRRIPEDIA. 



The parietes, (the basal margin of a small portion is represented at Tab. I, fig. 5#,) are per- 

 forated by large square longitudinal tubes : in the upper part these are filled up solidly without 

 transverse septa ; the longitudinal septa between the tubes are finely denticulated at their 

 bases, and the denticuli extend unusually close to the outer lamina. In very young speci- 

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

 septa, as in the case of other species of the genus ; but in medium and large-sized 

 specimens, there are between such ribs from one to four smaller ribs, which do not 

 correspond with any longitudinal septa ; these 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 (upper in fig. 5b) lamina of 

 the walls than there are longitudinal septa. As the parietes rest on the basis, the cir- 

 cumference of the latter becomes marked in a very peculiar manner (fig. 5c), by the basal 

 edges of the parietal septa. Hence the basis of this species can be distinguished from that 

 of every other sessile cirripede : its circumference is plainly impressed by the main parietal 

 septa which connect the inner and outer laminse of the walls ; and between these marks 

 there are two or three smaller impressions of the so-called representative septa, which do 

 not extend beyond the impression of the basal edge of the inner lamina. The upper sur- 

 face of the middle part of the basis (more especially when slightly disintegrated) is faintly 

 striated in radiating lines, of which the stronger lines are prolonged from the circumferential 

 marks left by the main parietal septa, and the weaker lines from the marks left by the 

 representative septa. 



Dimensions. — The largest recent specimens which I have seen from great Britain or 

 Ireland, have been 1*3 of an inch in basal diameter: in Mr. Cuming's collection, however, 

 there is one much depressed specimen from the Shetland Islands, 2 1 in basal diameter; 

 a regularly conical specimen from the coast of Massachusetts attains a nearly equal 

 diameter. But out of the glacial deposits in the Isle of Bute, several specimens 

 have this same diameter, namely, two inches, and are even more steeply conical, being 

 1*85 in height; some glacial specimens from Uddevalla and Canada, in Sir C. Lyell's 

 collection, are 1*7 in basal diameter. Hence it appears, as we shall presently see is 

 likewise the case with B. crenatus and Hameri, that northern specimens, and those from 

 the United States and from the Glacial deposits, often exceed in dimensions those now 

 living on the coasts of Great Britain and Ireland, or those found in the Crag. 



This species is very common in the glacial deposits of Uddevalla, of Skien in Norway, 

 and of Canada, and is associated with the same species, namely, B. crenatus and Hameri, 

 as in the living state : I have seen, also, as just stated, specimens from the same formation 

 in the Island of Bute, Scotland. I have examined numerous specimens from the Marn- 

 maliferous Crag, and a few from the Red Crag of England. I owe to the kindness of 

 Mr. J. de C. Sowerby an inspection of the original specimens of B. tesselatus of the 

 Mineral Conchology, which is certainly the present species. 



