THE SESSILE BARNACLES. 213 



evenly arranged, and continuing nearly to the end of the rami. 

 Cirrus vi has the segments much wider than long, bearing three 

 long pairs and one short pair of spines, with an intermediate dense 

 group of rather long bristles. There is a narrow band of minute, 

 erect spinules along the distal suture, Avidening into a large patch 

 anteriorh\ These spines are A^ery minute. 



The penis is aljout 30 mm. long, not quite as long as the sixth cirri, 

 and has the usual basi-dorsal point. 



This is the north Pacific representative of B, Jimmerl of the north 

 Atlantic. While closely related, the two species differ in many 

 details, and no annectant individuals have been found among the 

 very long series of each which I have examined. The chief differ- 

 ences are as follows: B. evermmvtu is more solid, more roughened, 

 and attains a far greater size than B. JmiiierL The summits of the 

 radii are very much longer and more oblique. The parietes are 

 not ribbed internally below the sheath, and the ribbing at the base 

 is of a wholly different character. The basal lamellae are not in the 

 least denticulate, and are very much more numerous. The periphery 

 of the basal plate is smooth, or only very indistinctly denticulate. 

 The scutum is flatter, not longitudinally striate, and the articular 

 ridge is lower and not angulate. The spur of the tergum is nar- 

 rower, the furrow running to it deeper and narrower, and the scutal 

 edge of the valve is much straighter. The maxilla has no notch 

 below the upper pair of spines, and the segments of cirrus vi have 

 no posterior lateral patches of spinules. 



B. evermanni is a distinctively cold-water barnacle, the data in 

 hand indicating a range of only about 13°, from 35.9° to 48.8° ^ F. 

 It is probably to be regarded as a member of the Bering 8ea fauna, 

 which spreads southward on both sides, in the cold waters of the 

 Kuril Islands and the inside passages of southern Alaska, which are 

 colder tlian the ocean outside. 



In habit of growth it resembles the large forms of B. hanoeii, 

 growing solitary or in branching candelabral forms, one barnacle 

 upon another. In Bering Sea nearly all were upon dead gastropod 

 shells or on others of their own species. No other species of Balanus 

 was found associated in the same groups, except that on one or two 

 individu.als from Bering Sea I found a few very minute, recently 

 attached barnacles, which I suspect to be infants of Balanus 

 crenatus. 



In the type lot of B. evermanni^ from the inland waters of south- 

 ern Alaska, the radii are wide in the adult stage, and the spur of 

 the scutum is about one-fifth the total length of the valve. In those 



■ The bottom temperature was not given for Station 4792, but as the surface temperature was 42° F., 

 it probably falls under 40° F. Only in tlioinland passages of southern Alaska was the temperature above 

 4(r F. 



4729°— Bull. 93—16 15 



