264 DISCOVERY REPORTS 



An examination of the material shows clear morphological differences between the two 'forms'. 

 Specimens of the 'long form' agree in structure with those described by Skogsberg (1920) from his 

 Antarctic material. The 'short forms' agree in structure with the material from the Mediterranean 

 described by Muller (1894) as C. rotundata. 



As Skogsberg (1920) has pointed out, the form of the shell is a characteristic feature of the species 

 of Conchoecia. This differs markedly in the two 'forms' considered here. The 'long forms' have a 

 greater ratio of length to depth and their greatest depth is anterior to the middle of the length, as 

 opposed to posterior in the 'short forms'. They have, in the material so far examined, a length of 

 1 -4 mm. or more, as opposed to 0-8-0-9 mm. in the case of the 'short forms '. Although the form and 

 spacing of the spines of the principle (V) seta of the male antennule is similar in the two, the 'long 

 forms' have 14-15 pairs whereas the 'short forms' have 9-10 pairs. The clasping organ of the endo- 

 podite of the right male antenna in the ' short forms ' is similar to that of C. kyrtophora or C. naso- 

 tuberculata, being sharply angled rather than smoothly curved as in the case of the ' long forms '. The 

 frontal organ of the male is similar in the two but the ' long forms ' have a dorsal insection which is 

 absent in the 'short'. 



Through the kindness of the authorities of the British Museum (Natural History), it has been 

 possible to re-examine Fowler's material from the Bay of Biscay. His stage I of C. rotundata agrees 

 with the 'long forms' and his stage II with the 'short forms'. 



It is clear that the two 'forms' are separate species, the 'short form' typical of the Mediterranean 

 and warmer waters of the Atlantic, the ' long form ' characteristic of the Antarctic and colder water, 

 at least in the Atlantic. The problem of specific identity remains. Both these species have previously 

 been ascribed to C. rotundata Muller. The original description (Muller, 1890) is inadequate even in 

 respect to diagnostic characters. On the basis of the described and figured outline of the shell and the 

 ten pairs of spines on the principal seta of the male antennule, together with the length of 1-15 mm. 

 as opposed to 1-4 mm. or more in the 'long forms ', it is clear that the latter are specifically distinct and 

 must be renamed. Morphological differences between the 'short forms' and the type description of 

 C. rotundata are slight and may or may not be significant. The length of the specimens under con- 

 sideration, as well as that of Midler's Mediterranean material, is less than that of his Pacific material. 

 The shape of the male frontal organ in the original description more nearly resembles that of the ' long 

 forms'. It would therefore seem preferable to treat the two 'forms' as distinct species. 



Muller (19 1 2) included Halocypris punica Scott (1894) as a possible synonym of Conchoecia 

 rotundata and it is necessary therefore to consider the possibility of this name being applicable to 

 either species. As Skogsberg (1920) has pointed out, the original description is of a specimen differing 

 so much that it is unlikely to be a synonym of C. rotundata. Dr J. P. Harding of the British Museum 

 has very kindly examined the type material. The tube contains the shell of the animal described by 

 Scott, together with other obviously unrelated material. It is clear that it differs so widely that it 

 cannot be the same species as either C. rotundata or the two species considered here. 



The specific name C. rotundata should thus, for the present, be restricted to the Pacific material 

 described by Muller (1890, p. 275, pi. xxvm, figs. 41-3; pi. xxix, fig. 44). The other two species 

 have been named as follows: 



Conchoecia skogsbergi n.sp. ('long forms'). 



C. rotundata (part) Muller, 1906, p. 83 (part); pi. XVII, figs. 25-9 (not 23-4); (?)figs. 3°~4- 



C. rotundata (Stage I) Fowler, 1909, p. 273; pi. 23, fig. 206; pi. 24, figs. 205, 215. 



C. rotundata (part) Muller, 1912, p. 77. 



C. rotundata Skogsberg, 1920, p. 649 et seq.\ figs, cxxn and cxxiii. 



