60 BULLETIN 60, UNITED STATES NATIONAL MUSEUM. 



The two latera meet below the carina. From the umbo a conical, 

 raised, and radially costulate area extends to the basal margin. 



The peduncle is very short, compactly covered with narrow trans- 

 versel}" elongate scales, in eight rows of about eight scales each. 



Length of the oapitulum 15.3, breadth 7.5 mm. Length of the 

 peduncle 5 mm. Length of the carina 13.5, diameter at base 2.2 nmi. 



The mandible (Plate V, fig. 15) has four teeth, unequally spaced, 

 the lowest one ending in a group of about five small spines. The max- 

 illa has a pair of stout spines at the upper angle, the face notched 

 below them, with a double row of spines. 



The first cirrus has unequal rami of eight and nine segments, those of 

 the anterior ramus wider and shorter. It is densely hairy. The second 

 cirrus is like those following, but a little shorter. The sixth cirrus 

 has segments with four pairs of spines, the anterior one in each pair 

 longer. The upper or distal group on each segment usuall}" has three 

 large spines instead of two. The posterior side has a pair of spines 

 at the distal angle, one large, the other small, and on the outer cirrus 

 there is a spine nearly midway between sutures. Fig. 9 of Plate IV 

 represents an intermediate segment from the outer ramus of the sixth 

 cirrus, the anterior side toward the right. 



The caudal appendage (Plate IV, fig. 13) consists of five long seg- 

 ments and terminates in a group of three very long spines and one or 

 two small ones. Length including spines is about 2.8 mm. 



This species is related to S. talismani Gruvel and its allies, but 

 difl'ers by the very weak or hardl}^ noticeable radial sculpture. Its 

 nearest relative is S. semisculptum^ a form in which the entire carinal 

 latus is radially sculptured, and the carina has wider sides, stouter 

 lateral ribs, and angular, V-shaped stride on the roof. 



Nine individuals from five stations between Cape Hatteras and 

 Marthas Vineyard are in the collection. One of three in the type lot 

 has the inframedian latera on both sides bent strongly towards the 

 ventral margin, over the rostral latera (fig. 26 a). In another example, 

 from Station 2728, these latera are bent towards the dorsal border, 

 overlying the carinal latera. It would seem that, since these plates 

 are crowded out of their normal place, their growth is likely to be 

 uneven, and a large proportion of abnormal individuals results. 



The largest individual has a capitulum 18 mm. long (Station 2728); 

 but this size is attained at no other station, and some apparently mature 

 capitula are only 12 mm. long. 



This species is named for C. W. Aurivillius, author of an excellent 

 paper upon North Atlantic, Arctic, and Oriental cirripedes. (Fig. 26a, J.) 



