164 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



minute but acute denticles on one side, one barely perceptible 

 prominence bearing several minute points and short hairs on the 

 other (fig. 4Se). Mandibles and maxillae as usual in B. ~balanus. 



Cirri. Cirrus i with rami of 19 and 12 segments; ii with 14 and 

 13 segments in the type. In a specimen from Albutross Station 2864 

 there are : Cirrus i, 21 and 12 ; cirrus ii, 15 and 12 segments. Cirrus 

 iii has both rami provided with numerous spinules (fig. 4S&) want- 

 ing on the distal segments. Cirrus iv has many spinules near the 

 distal sutures of the segments (fig. 48a). Cirrus v has similar 

 but fewer spinules. Cirrus vi has four pairs of spines, the third 

 pair small, fourth pair minute, wanting on part of the segments. 

 There are a few minute accessory spines at the bases of the pairs, 

 and some small ones near the distal sutures (fig. 48c). 



The penis is longer than in B. lialanus, but not so long as in 

 B. rostratus. It has the usual point near the base. 



By the small number of spines on the posterior cirri, this form 

 approaches some British specimens of typical B. balanus. 1 It has 

 decidedly shorter spines on the posterior sutural angles of the seg- 

 ments, and the penis is longer. The parietes are not ribbed, in con- 

 siderable numbers seen. In the series of B. ~balanus from Bering 

 Sea, the parietes are rugose or ribbed, and the cirri are conspicuously 

 more spinose. 



A long series growing on Pectens, from which the type lot was 

 selected, was submitted by Dr. Homer Wheeler. A small lot, prob- 

 ably from the same localitv, is in the United States National Museum 



/ / / 



collection, received from the University of Kansas; and a lot was 

 taken by the Albatross at station 2864, latitude 48 22' north, longi- 

 tude 122 51' west, in 48 fathoms, bottom temperature 47.7 F. 

 (Cat. No. 48021, etc., U.S.N.M.) 



It lives mingled with B. rostratus heteropus, and the two can not 

 be discriminated externally. The easiest and most reliable way to 

 tell them apart is to file the parietal face enough to expose the tubes, 

 which are large and unobstructed in B. b. pugetensis, much smaller 

 and transversely septate in B. r. heteropus. 



SERIES OF B. CRENATTJS. 



White Balani, with the basis poreless; terga not beaked, not pro- 

 jecting conspicuously above the scuta, arid without a furrow to the 

 spur; scuta without longitudinal striation. Maxilla with one longer 

 or larger spine near the lower angle. 



Near the group of B. balanus, differing chiefly by the opercular 

 valves and by the absence of spinules on the segments of the peduncles 



1 On the segments of B. r. pugctensis corresponding to those I have figured for B. "balanws 

 there are only three pairs of spines. Another pair appears nearer the distal end, as usual 

 in Balanus. 



