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



the largest specimen, however, of this species dredged. These mandibles are very long 

 and slender, three-jointed, little shorter than the proboscis. The third joint terminates 

 in a pair of small and slender pincers. 



Of the palpi the third joint is longer than the fifth. Of the last three joints the 

 first is extremely small and broad (PL IX. fig. 7), and the ninth is inserted, not into 

 tlie middle of the front part of that joint, but quite laterally. This ninth joint itself 

 is cylindrical, and more than twice as long as the foregoing, whereas the tenth is a little 

 more slender and still longer than the ninth joint. 



The joints of the comparatively long ovigerous legs have characteristic proportions 

 in all the species of the genus Colossendeis. The claw at the end of the tenth joint 

 is very small. The denticulate spines on the last four joints are not numerous, the 

 number of rows not exceeding four. Of these two are very regular, with the spines 

 placed close to one another, but those of the two other rows are much more irregularly 

 scattered over the remaining part of the inner surface of the joint (PI. IX. fig. 8 ; 

 PI. X. fig. 7). 



The lengths of the several legs of one and the same specimen only show slight 

 differences. The third leg is, in the three specimens I have examined, the longest, and 

 measures nearly three and a half times the length of the body. The claw is very long, 

 still longer than the second tarsal joint. Genital pores are present on the second joint 

 of every leg. As to the sex of the three specimens dredged during the voyage of 

 H.M.S. Challenger, I have only been able to ascertain that the specimen with mandibles 

 is a male. 



The body and legs are almost entirely smooth ; small hairs are only to be observed 

 on the last joints of the palpi. 



Habitat. — This species was dredged between the Cape of Good Hope and Kerguelen 

 Island. 



Station 146. December 29, 1873. Lat. 46° 46' S., long. 45° 31' E. Depth of the 

 sea, 1375 fathoms. Temperature of the bottom, 1-5° C. Bottom of the sea, globigerina 

 ooze. 



Station 147. December, 30, 1873. Lat. 46° 16' S., long. 48° 27' E. Depth, 1600 

 fathoms. Bottom temperature, 0-8° C. Bottom of the sea, globigerina ooze. 



Observations. — To this species Colossendeis media and Colossendeis brevij^es, which 

 I shall describe further on, are closely allied. The occurrence of mandibles in one of 

 the specimens of this species is very interesting. Although larvae of any species of 

 Colossendeis have never been observed, they doubtless are furnished with three pairs of 

 cephalic appendages. Of these the adult animal has always lost the first pair- ; and 

 whenever, as in the case in question, this first pair is observed in the adult animal, it 

 must be considered as a case of atavism, showing that the loss of mandibles in the 

 adult animal has been comparatively recent. 



