Chilton. — Ceina, an Aberrant Genus of the Talitrulu 11.9 



genus Ceina, Delia Valle gave a brief description which may be translated 

 as follows : " Upper antennae a little longer than the peduncle of the lower. 

 Second gnathopods of male chelate. Third uropods represented by peduncle 

 without rami. Telson divided." He pointed out that the species was 

 deserving of further investigation, particularly with regard to both pairs of 

 maxillae and to the terminal uropods. In this paper I endeavour to supply 

 the information that Delia Valle considered was necessary, and I regret that 

 various circumstances have prevented its being supplied earlier. 



In 1906 (p. 554), in his revision of the Amphipoda for Das Tier- 

 reich, Stebbing described the genus as follows : " Antenna 1 longer than 

 peduncle of antenna 2. Maxillipeds, finger of palp broad, subtriangular. 

 Gnathopod 1 in male and female and gnathopod 2 in female subchelate, 

 small. Gnathopod 2 in male much larger, subchelate or (in maturity) 

 chelate. Uropod 3 tubercular, without rami. Telson partially cleft." 



There are also one or two points not mentioned in this description 

 owing to their having been previously undescribed which are worthy of 

 being included in the generic description. Thus, in the mandibles the 

 usual molar tubercle is quite absent, and appears to be represented or 

 replaced by a peculiar lappet on the inner surface directed backwards 

 towards the base of the appendage. In the first maxilla the palp is absent 

 or very minute, as in most of the species of Orchestia ; the outer lobe is of 

 normal structure, but the inner lobe is very small, barely half as long as 

 the outer, and without the usual two plumose setae. It thus difiers from 

 the character of this maxilla as laid down by Stebbing for the family 

 Talitridae, where he says " maxilla 1, inner plate slender, tipped with 2 

 plumose setae " ; Sars (1895, p. 21) also gives this as one of the characters 

 of the family, and the diagnosis of the family will therefore need to be 

 slightly modified to include the genus Ceina. The second maxilla and the 

 maxillipeds are fairly normal ; but the large chelate second gnathopod of 

 the male is a distinctive feature, and the terminal uropods are peculiar, 

 being represented only by a short tubercle, which probably is the modified 

 peduncle without rami. In this last character Ceina differs markedly from 

 Hyale and approaches the allied genus Chiltonia, where the terminal uropods 

 are represented by a single joint. 



The generic diagnosis and the synonymy of the species may be given as 

 follows : — 



Ceina Delia Valle. 



Ceina Delia Valle, 1893, p. 530 ; Stebbing, 1899, p. 397, and 1906. 

 p. 554. 



The genus may j)erhaps be defined as follows : Mandible without defi- 

 nite molar tubercle. First maxilla with palp absent or vestigial, inner lobe 

 small and without jjluraose setae. First gnathopoda small and subchelate 

 in both sexes ; second gnathopoda large and chelate in the male, subchelate 

 in the female. Third uropoda represented by a small rounded lobe. Telson 

 formed of a thick plate, partially cleft. 



It is not easy to assign a definite position to this genus among the allied 

 genera of the family. In many of the characters it more or less resembles 

 Hyale, but it distinctly difl^ers from this genus in the mandibles, first 

 maxillae, the vestigial third uropoda, and the telson. In the last points 

 it shows some approach to the genus Chiltonia, but the special character 

 of the mandibles and of the inner lobe of the first maxillae are different 

 from anything known to me among other Talitridae ; the vestigial nature 



