2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



ing the visceral mass with the mantle. In Briar osaccus the mesentery- 

 is comparatively narrow as in the Sacculinidae (fig. 3). 



The type specimen of the genus, described below, may be character- 

 ized as a distinct species especially by the structure of the chitinous 

 covering of the mantle. 



BRIAROSACCUS CALLOSUS, new species 



Type.— C?ii. No. 62304, U.S.N. M., on Lithodes agassizii Smith, 

 "Albatross" Sta. 2666 (off Fernandina, Fla., 270 fathoms) orSta. 2677 

 (off Cape Fear, N. C, 478 fathoms), 1886. 



External cuticle thick and callous, with grooves and shallow pits. 

 The surface is covered with small excrescences, which have a length 

 of approximately 9^ and form a dense covering of the outer layer. 



~^>.. 



\ 



Figure 1.— Bkiarosaccus callosus, right surface. Natural size 



Internal cuticle with retinacula of large size, containing numerous 

 spindles, which vary in length from 15/x to 55iu. 



The specimen has a length of 98 mm, its height attains 53 mm, 

 and the thickness amounts to 31 mm. As compared with all other 

 Ehizocephala hitherto known it really is a gigantic animal (fig. 1). 

 The thick external cuticle possesses a number of grooves which spread 

 from the stalk toward the ventral region of the parasite. Between 

 these grooves and especially at the ventral region the surface of the 

 mantle shows numerous small depressions, giving the surface a 

 dotted appearance. The stalk is surrounded by a strong shield, 

 consisting of chitin of a harder kind and of a darker color than the 

 remainder of the external cuticle. The mantle opening is found at 

 one side of the animal, which consequently has to be regarded as the 

 anterior pole. In Figure 1 it is visible, though rather indistinctly, 



