200 balaniDjE. 



radii ; and this is not very infrequent in young shells. Exteriorly the 

 radii are generally smooth, but sometimes finely ribbed horizontally, 

 owing to the projection of the septa. The alee have their sutural edges 

 smooth ; their summits are usually parallel to the basis, but they are 

 often much broken ; in var. zebra, however, in every specimen which 

 I examined, the summits were oblique. The sheath varies much in 

 colour : in var. occator, and in a less degree in var. intermedium and 

 var. d" Orbignii, the portion lining the rostrum and lateral compart- 

 ments is much darker than the other parts of the sheath. The Basis 

 generally has a thick, underlying, cancellated layer. Sometimes the 

 basis (PI. 1, fig. b) is irregularly cup-formed. 



Mouth : labrum with four or six minute teeth : mandibles with five 

 graduated teeth ; inferior point more or less spinose. Maxillae, either 

 with or without a small notch, beneath the upper pair of spines ; in 

 the lower part there are two spines longer than those immediately above 

 them. Cirri, the first pair has the rami unequal, in the proportion of 

 about 19 segments in the longer ramus, to 16 in the shorter. The 

 segments in the latter have their anterior surfaces very protuberant. 

 The second pair is short, with the anterior surfaces of the segments 

 protuberant. On the thorax (PI. 25, fig. 1), on each side, at the bases 

 of third pair of cirri, there is a projecting membranous plate fringed 

 with fine bristles. The three posterior pairs have their segments shield- 

 shaped in front, generally bearing four pairs of spines, of which the 

 lower pair is minute ; between these pairs there are some minute spines. 

 In some young specimens from the Cape of Good Hope, and in var. 

 concinniiSy I found six pairs of spines on the segments of the posterior 

 cirri. 



Geographical Distribution. — This species is extremely common over 

 the whole of the warmer seas. It rauges from the Island of Madeira 

 to the Cape of Good Hope, and on the west coast of America, from 

 Monterez, in lat. 37° N., in California, to Peru. It is attached to rocks 

 and sub-littoral shells, to floating timber, to kelp, and to Lepas anati- 

 fera. It is attached in wonderful numbers to ships' bottoms arriving 

 at our ports, from West Africa, the West Indies, the East Indian 

 Archipelago, and China. It is generally associated with B. amphitrite 

 and awaryllis. I have already stated that, on the bottoms of vessels, 

 the different varieties are generally grouped together ; and this makes 

 me believe that they are local. In Mr. Stutchbury's collection there 

 are numerous specimens taken from a ship which first went to the west 

 coast of Africa for guano, and then to Patagonia for the same object, 

 and it was interesting to see the manner in which numbers of B. 

 gsittams, a Patagonian species, had become attached on the African B. 

 tintinnabulum. The varieties from the west coast of America seem 

 eminently peculiar; we there find var. coccopoma and concinnus ; and 

 a blueish, rugged variety, with peculiar opercular valves. 



Geological History. — I have seen specimens in Mr. S. Wood's col- 

 lection from the Red Crag of England, which, though not accompanied 

 by opercular valves, I cannot doubt belong to this species. The speci- 

 mens named by Air. Sowerby, in the ' Mineral Conchologv,' as B. 

 rrassus, and which I have seen through the kindness of Mr. .1. de C. 



