80 THE VOYAGE OF H.M.S. CHALLENGER. 



Length of the capitulum, 31 mm. 



The 'peduncle is cylindrical, narrow, short (10 mm.); the scales are not calcareous, but 

 vet their margins are very distinct. They form eight longitudinal rows, each containing 

 aboul eighl scales. 



A single specimen of this species was taken at Station 198, October 20, 1874 ; lat. 

 2° 55' X., long. 124" 53' E. ; depth, 2150 fathoms; bottom temperature, 3°7 C. ; 

 bottom, red clay. 



Observations. — I have not been able to investigate the structure of the mouth, of the 

 cirri, of the caudal appendages, &c. With regard to the complements! males, I found on 

 the interior surface of the right-hand scutum five of them attached close to the occludent 

 margin. I have figured one of them (PI. VIII. fig. 11). Their size is 1*3 mm. Their 

 form is elongate, having the shape of a pear. The small antennae (an) are distinctly to 

 be observed, and consist of one segment only. The body is covered by a double wall, 

 the exterior one forming a kind of mantle. Its outer surface is clothed with very small 

 bristles, and at one extremity, the more swollen one, the external wall has an opening. 

 The only organ which is well developed is the testis (t.), with its receptaculum seminis (r.s.). 

 The testis is very large and heart-shaped ; the receptaculum seminis is relatively small, 

 and consists of an oval sac; at one extremity it communicates with the testis, at the 

 other with the vas deferens. I tried in vain to distinguish where this duct opened ; 

 probably it is close to the opening of the mantle. 



The specimen of Scalpellu/m compressum contained eggs. These are not very 

 numerous, but relatively large. Their shape is oval, their length about 0'8 mm. 



C. Species with the carina simply bowed. 



a. With a sub-carina. 



Scalpellum mutum, n. sp. (PI. III. fig. 19; PI. VIII. fig. 12). 



Surface of the valves smooth, not covered by membrane. Valves thirteen. Carina 

 simply 1 lowed, very short. Umbo of the carina at the apex. A distinct sub-carina and a 

 distinct rostrum are present. Only two lateral valves of the lower whorl at each side. 



Of this extremely interesting species three specimens were taken at Station 170. 520 

 to G30 fathoms, and one specimen at Station 78, 1000 fathoms. 



The capitulum is flat and elongate, and consists of thirteen valves. Besides the carina 

 and the three pairs of upper latera, there are a rostrum, a sub-carina, and two pairs of latera 

 of the lower whorl. Most of the valves have an elongate and pointed shape; the umbo 

 ol the rostrum projects outwards. The capitulum is not covered by membrane ; near 

 the base, however, small parts of a chitinous covering are still adhering to the valves, 

 fhe scutum is parallelogram-shaped, and divided into two triangular parts by a slightly 



