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



Encyclopaedia Britannica, has written a short description, accompanied by figures, of a 

 small Isopod from Flinders Island, Bass Strait, under the MS. name given by White 



There appears to be no doubt that Bregmocerella, a new genus lately instituted by 

 Haswell, is identical with Ceratocephalus, and it is necessary, therefore, to cancel HaswelTs 

 name, as Ceratocephalus has evidently the priority. Both descriptions, which are very 

 brief, refer only to the male. As the Challenger obtained a great number of specimens, 

 including females, I have thought it worth while to give a more detailed description of 

 this Sphreromid, which is to be distinguished from any of its allies by the long " horns " 

 upon the head and the greatly elongated antennae; in other respects Ceratocephalus does 

 not depart far from the structure characteristic of the Splucromidae. 



Ceratocephalus gray anus, White. MS. 



Ceratocephalus grayanus, White, MS., Woodward, Art. Crustacea, Encycl. Brifc., ed. 9, p. C59. 

 Bregmocerdla tricomis, Haswell, Proc. Zool. Soe. N.S.W., vol. ix. p. 100 1. 



This species is represented by a large number of individuals from Port Jackson, and 

 from localities further to the south, at Station 161. The individuals from Port Jackson 

 are all of small size, the largest specimen measuring 17 mm., including the rostrum. 

 Three specimens were dredged at Station 161, two of which measure as much as 

 28 mm. in length; apart from the larger size of the latter there is no difference 

 between the individuals from the two Stations, at least no difference that would seem 

 to necessitate their separation as distinct species. 



This species exhibits a well-marked sexual dimorphism. 



The males are distinguished from the females by the possession of three long horns, 

 projecting from the anterior region of the body, of which there are only the faintest 

 indications in the females. The antennules of the male are longer than in the female; 

 other differences will be apparent from the following description of the two sexes. 



Descrip>tion of the Male. — The body is capable of being contracted into a ball as in the 

 genus Spliseroma. The head is narrower than the first segment of the thorax and only 

 a very little longer; the dorsal surface is much sculptured. Anteriorly the head is 

 prolonged into a long spine, which is wide and triangular at the base and gradually 

 narrows towards the extremity, becoming slightly thickened just at its extreme end ; the 

 spine does not project straight from the head but is curved upwards ; it arises from the 

 inferior surface of the head, its posterior extremity being excavated for the upper lip ; 

 on the dorsal surface of the head, just above the spine and lying between the antennary 

 appendages, is a deep depression ; from the margins of this two ridges, one on either side, 

 pass to the eyes and form the anterior margin of the head ; in front and to the inside 

 of the eyes this ridge gives off a strong spine on either side, not more than half the 

 length of the median spine ; each of these spines is somewhat curved ; the proximal half is 



