196 M. A. Gruvel on a new 



Capitulum. — The capitulum, entirely devoid of plates, is 

 covered with a thick chitinous envelope, extremely trans- 

 parent even after prolonged immersion in alcohol, and orna- 

 mented with transverse folds which are especially numerous 

 near the orifice. It is swollen towards the median and 

 lateral regions, and then strongly retracts to form a kind 

 of short, tubular duct in which the cirri are set. The 

 capitulum has no dorsal crests, but simply a slight continuous 

 ridge which follows the median dorsal line from the opening 

 of the capitulum to the commencement of the peduncle. 



Seen in profile, the general form of the capitulum is that 

 of a semicircle, of which the anterior part, forming the base, 

 is straight, and the posterior part regularly curved. 



The dimensions of the capitulum of the largest specimen 

 are as follows : — Height 20 mm., breadth 18*50 mm., thick- 

 ness 8*5 mm. 



Peduncle. — The peduncle continues the capitulum without 

 a break. At first broad, it contracts and is almost cylin- 

 drical towards its middle part ; then it broadens again to its 

 base to form its surface of attachment. The cuticle is the 

 direct prolongation of that of the capitulum. 



This cuticle of the capitulum and peduncle presents some 

 interesting features. It is composed of chitinous processes 

 separated by somewhat irregular spaces. Some are wide at 

 their base, and their summit terminates in three or four 

 pointed branches which are recurved and divergent, forming 

 hooks (PI. VIII. fig. 2) • others are shorter and simply conical 

 (fig. 3). These processes have nearly the same height in 

 the same zone, and this height varies from 4 - 8 //. to 24 /£. 

 Near the middle of each of these zones is a sensory bristle 

 receiving at its base a nerve-filament which is very distinct, 

 long, slender, and terminates in a fine point. The average 

 length is from about 95 to 100 /n (fig. 4). 



In general each zone of many-pointed hooks is surrounded 

 by a zone of conical spines, and it is usually also in the zone 

 of hooks that the sensory bristle is placed. 



The opening of the capitulum is heart-shaped, presenting 

 on the median dorsal line a circular protuberance delimitating 

 a depression and not a true canal. 



Mantle. — The mantle which clothes the chitinous cuticle 

 on the interior is composed of the usual two epithelial layers, 

 including between them two muscular layers, the one longi- 

 tudinal, the other oblique, crossing at various angles and 

 together forming a kind of very elegant tessellation, these 

 bundles being separated one from another by a distance of 

 about 70 >fi. There is, moreover, quite a system of branching 



