170 



BULLETIN" 93, UNITED STATES NATIONAL MUSEUM. 



39 fathoms, measure: length 58 mm., diameter 12 imn., and length 



40 mm., diameter 17 mm. The radii are narrow. 



In a few specimens from Albatross station 2462 the spur of the 

 tergum is quite narrow (fig. 62(?). The scutum is of the usual nar- 

 row form of Newfoundland Bank crenatus. 



In a series from Sable Island, off Nova Scotia, on bark (probably 

 from a stake or pile) the form and size are similar, but the ribs are 

 split into numerous irregular riblets. The peritreme is acutely 

 toothed. The articular ridge of the scutum projects beyond the 

 tergal margin more than in the Grand Banks form, and the spur of 



Pig. 53, — Balanus crenatus. a, h, scutum and teugum of specimen from Sable 

 Island, from group pl, 40, fig. 3. c, scutum of specimen from the fishing banks. 



the tergum is a little longer, but otherwise the opercular valves are 

 similar (pl. 40, fig. 3 ; text fig. 53«, h). 



The common forms from shallow w^ater on the New England 

 coast are not distinguishable from English examples. A group from 

 Vineyard Sound is figured (pl. 39, figs. 2-2(7, 3, 5, Gat. No. 48027-8, 

 U.S.N.M.) showing the columnar form, growing on a pebble, and 

 the conic form, on Mytllus edulis. The opercular valves of the 

 columnar form do not differ materially from those of the smooth 1 

 form figured, except that they are larger and thicker, the interior of 

 the tergum (fig. 3) being extensively granulated. Specimens, 

 growing on Mytllus^ from an iron buoy. Gay Head, Marthas Vine- . 

 yard (pl. 39, figs. 2-2c), are beautifully smooth and white, with thin 

 walls and regular, square tubes, 12 in the rostrum of one counted. 

 The opercular valves are rather thin, and the spur of the tergum is 

 farther from the basiscutal angle and narrower than is usual in 

 European crenatus. The scutum is concave externally, with a 

 broadly reflexed articular ridge. 



On the Newfoundland Banks, this species is most abundant on 

 Buceinum humphreysianuTn, donovani, etc., but also occurs in Chry- 

 sodomus, Tritonifusus, Pecten islandieus, Cyrtodaria, Serripes, 

 on crabs (Hyas), and on bowlders. It has been found in the 



i 



