7^ THE VOYAGE OF II. M.S. CHALLENGED. 



The capitulurn is robust, about twice as long as broad, and not very flat. It is 

 covered by a thin membrane, and the different valves are separated by broad chitinous 

 interspaces. A distincl white line divides these interspaces into two equal parts, and marks 

 the area of the different valves. Of these there are fourteen. The lines of growth 

 are uol distinct. 



The scutum is elongate quadrangular; it is somewhat broader near its base than in 

 the upper half. The umbo is at the apex, which slightly projects outwards, and which 

 has a triangular, recurved, and pointed form. 



The tergv/m is triangular. The occludent margin is much arched, hence the apex 

 is distinctly recurved. The inferior part is a little produced. 



The carina is bowed and internally concave ; the portion above the umbo is very short, 

 and not more than one-sixth of the total length. Since the roof is slightly convex, the 

 sides of the carina pass over into the portion above the umbo. 



The upper hit us is trapeziform, with the scutal margin slightly hollowed out and not 

 quite twice as long as the carina! margin. The apex is sharply pointed. 



The rostrum is small, triangular, wedge-shaped. 



The rostral latus is convex, four-sided, with the scutal and basal margins almost parallel 

 and slightly hollowed out. 



The infra-median latus is extremely small, triangular, with the umbo at the apex. 



The eariual latus is flat, four-sided ; basal margin nearly straight. Superior portion 

 of the carinal margin slightly hollowed out, inferior portion short, lateral margin 

 straight. The umbo is seated at the base of the carina and projects slightly outwards. 



Length of the capitulurn 1 3 mm. 



The peduncle is cylindrical, and has a length of 7 "5 mm. Very small and not 

 numerous calcareous scales are scattered over its surface. At the place of attachment the 

 foot of the peduncle grows wider. 



Mouth. — Mandibles with three teeth, and the inferior angle pectinated, almost as in 

 Scalp>ellum intermedium. Maxilla' (PI. VIII. fig. 9) with a rather deep notch behind 

 the first four spines, and a second less deep notch in front of the inferior angle. The 

 second maxilla? have the so-called olfactory orifices at the end of long processes. 



Cirri. — First pair with very unequal branches ; the anterior and shorter branch has 

 six rather broad segments, the posterior eight longer and more slender segments. The 

 outer surface of the segments is extremely hairy. Of the other cirri nothing very 

 characteristic has been observed. 



The caudal appendages (PI. VIII. fig. 10) are elongate and distinctly four-jointed ; 

 each segment bears two small spines at the extremity ; the fourth is crowmed by a tuft 

 of about five stouter and two smaller bristles. 



Penis short, rudimentary. 



Comple mental nudes not observed. 



