480 BALANIDJ2. 



Penis short, hairy, finely-ringed, with no projecting point at its 

 dorsal basis. Branchiae moderately large, nearly circular, not much 

 plicated. 



Fossil Specimens. — With respect to the Sicilian specimens sent me 

 by Dr. Philippi and Sir C. Lyell, I can see no difference whatever from 

 the recent specimens, excepting in their greater size and thickness ; 

 it must, however, be borne in mind that I have seen only half-a-dozen 

 recent shells. The one fossil scutum which I have seen is rather 

 broader than is usual with the recent, but I have seen one nearly as 

 broad. This species seems to have been extremely common when the 

 beds at Messina were deposited, and probably it attained a larger size 

 than it does at present. The compartments are always found separated, 

 which is easily understood, by the facility with which, as above 

 stated, recent specimens fall to pieces. 



2. Pachylasma aurantiacum. PL 20, fig. 1 a — 1 d. 



Shell tinged wiih orange ; viewed externally seems formed 

 of only four compartments, owing to the carino-lateral and 

 lateral compartments on each side being separated only by 

 an obscure fissure. 



Hab. — New South Wales ; apparently from deep water, attached to sand- 

 stone.* 



General Appearance. — Shell conical, smooth, w r ith a tinge of orange 

 colour ; orifice large, deeply notched, sub-triangular. Viewed ex- 

 ternally, the compartments in appearance are only four ; but on close 

 examination, the lateral compartments are seen to be divided by a very 

 fine fissure into two nearly equal compartments. The rostrum is 

 broad and flat, and when carefully exr.mined, it also is seen to be 

 divided by two fine fissures into three compartments ; of these the 

 middle one, or true rostrum, is a very little broader than the rostro- 

 lateral compartment on each side ; hence, on careful examination, the 

 shell is found to consist of eight compartments. The carina is much 

 compressed. The radii (in my one specimen) are not developed. The 

 carina, and the two lateral compartments alone, have alse; for the carino- 

 lateral compartments are too closely joined to the lateral compartments, 

 and the true rostrum is too closely joined to the rostro-lateral com- 

 partments, to have their alae developed. The four alae which are 

 developed, are very broad, widely exposed, and marked externally by 

 lines of growth. The basal diameter of my one, apparently old 

 specimen, is one inch. 



* I am indebted to Mr. Bowerbank for this unique and interesting species, 

 winch I have deposited in the British Museum. 



