212 DR. C. CHILTON ON THE SUBTERRANEAN 



longer than the fifth, widest in the centre, where its posterior margin is deeply cleft, and 

 in a dorsal view it does not extend quite to the sides of the pleon. It is apparently 

 clearly divided off from the telson, although this seems to be very exceptional in the 

 Isopoda. 



The surface of the whole body is smooth and bears a few short separate setae scattered 

 over it, especially on the dorsal surface. 



The upper antennoe (figs. 2, 3) are rather shorter than the lower; peduncle of three 

 joints : first joint the largest, with an " auditory seta " on its outer margin and one 

 or two simple setae at the extremity ; second joint about two-thirds the length of 

 the first and narrower, with two " auditory setae" and one or two simple setae at the 

 extremity ; third joint longer than the second, nearly as long as the first, extremity 

 bearing simple setae and one auditory seta. The remaining portion of the antenna appears 

 to represent the flagellum ; it consists of one very short, indistinct joint, followed by one 

 as long as the second joint of the peduncle ; this joint bears at its extremity a few simple 

 setae and about four or five " olfactory cylinders " ; it is followed by two or three very 

 minute joints, of which the first bears an " olfactory cylinder " and the last ends in a 

 small pencil of three very long simple setae. 



The lower antennoe (figs. 2, 4, 5) have the first joint very small, nearly rectan- 

 gular, broader than long ; this joint can be seen only when the antenna is viewed from 

 below, as in fig. 5 ; it is quite concealed in a view from above by the base of the 

 upper antennae. The second joint is large and broad, considerably longer than the first 

 joint of the upper antennae, which rests on the top of it in an oblique groove ; it bears a 

 minute seta at the extremity on the inner side. The third joint is short, narrow at the 

 base, more or less geniculate with the first, and bears one or two minute setae at the 

 extremity on the inner side. The fourth joint is twice as long as the third; it bears 

 several long setae at the extremity and one or two small ones on the inner margin. The 

 fifth joint is rather longer than the fourth, but slightly narrower ; at the extremity it 

 bears several simple setae, some of them very long, and three " auditory setae." The 

 remaining part of the antenna may by analogy be considered as the flagellum ; it consists 

 of one joint about as long as the second joint of the peduncle, and at its extremity a 

 minute joint ending in a pencil of long setae. 



Movth-parts. The mouth of Cruregens fontamis, like that of other Anthuridae, is 

 adapted for suction. It is situated near the anterior end of the head, and the various 

 parts project forwards and can usually be seen in a dorsal view between the bases of the 

 antennae. To form the sucking-apparatus the various parts are much modified, and 

 have coalesced to such an extent that I have found considerable dilficulty in deter- 

 mining the homologies of all the parts. My difficulty has been increased by the want 

 of the necessary works of reference. Spence Bate and Westwood give very little 

 information on the subject in their ' British Sessile-eyed Crustacea' [4]. Norman and 

 Stebbing [106], in their account of the " Isopoda of the ' Lightning,' ' Porcupine,' 

 and ' Valorous ' Expeditions," supply figures of the mouth-parts of some of the 

 Anthuridae, but, unfortunately, they give no description beyond the brief accounts 

 comprised in the generic diagnoses. I regret that I have not been able to consult 



