SYSTEMATIC REPORT m 



In A. ohlinii the posterior margin of the telson is very slightly emarginate and is armed with three 

 pairs of long spines, the innermost of which is only very slightly longer than the two outer pairs, 

 but as a result of the emargination of the margin their tips reach the same level. There is no gap in the 

 median line. The only specimens which we had at our disposal, when I figured the telson (W. M. 

 Tattersall, 1951, fig. 45 c), were badly damaged and not one had a complete set of spines around the 

 apex, but the scars, where they had been broken off, proved that they had formed a complete sequence 

 with the graduated spines of the lateral margins. The size of the scars of the innermost spines indi- 

 cates that these had been large and there was no trace of the small median spines which are so charac- 

 teristic a feature of obtusa. I do not think it likely that such tiny median spines would have been 

 broken off had they ever been present. 



The Discovery material is in bad condition and the larger spines arming the apex of the telson are 

 often missing, but the tiny median pair is present in all the specimens. The spinulation of the eyeplates 

 is another useful guide to the identification of the species. In A. crozetii, the only other species from 

 southern waters, the eyeplates are smooth and in A. ohlinii there is very fine, sparse spinulation, 

 confined to a small region at the extreme antero-lateral angle of each plate. 



Distribution. The types were taken on the Patagonian Shelf to the west of the Falkland Islands in 

 403 430 m. and a single adult female was captured in the Strait of Magellan in a night haul with a net, 

 fishing at 300 m., which failed to close. It would thus appear that A. obtusa is a mesoplanktonic form 

 inhabiting more shallow waters than either of the other species of the genus. 



Genus Paramblyops Holt and Tattersall, 1905 

 1905 Paramblyops Holt and Tattersall, p. 124. 



Remarks. This genus, closely resembling Amblyops, was instituted for the reception of a new species, 

 Paramblyops rostrata Holt and Tattersall, which differed from Amblyops as follows: (1) Carapace of 

 only moderate size, its anterior margin produced into a long, acutely pointed rostrum partially covering 

 the eyeplates. (2) Eyes of the same degenerate form as in Amblyops, consisting of separate, rounded 

 flat plates without visual elements or pigment, but with the outer, distal angle of each drawn out 

 into a sharp process. (3) Telson large, linguiform with a broadly truncate apex armed with spines but 

 no median setae. Tattersall (191 1 b, p. 48) added a second species, Paramblyops bidigitata, to the genus, 

 its main point of difference being that there were two finger-like processes on each eyeplate. 



Three specimens from station 181 and two from station 182 in the Discovery collection must 

 undoubtedly be referred to a new species of this genus. They show some small differences from the 

 original definition of the genus and a re-examination of specimens of P. rostrata has revealed one 

 important feature overlooked by Holt and Tattersall. In his description of P. bidigitata Tattersall 

 (191 1 b, p. 48) described sternal processes in the males and young females. Holt and Tattersall (1905) 

 had not mentioned any such processes in P. rostrata and Tattersall, when summarizing the differences 

 between the two species, cites the presence of sternal processes in bidigitata as one of the distinguishing 

 characters of the species. When I found that similar processes were present in the new species, P. brevi- 

 rostris, I re-examined specimens of P. rostrata in my husband's collection and found that in all the 

 males and in young females, in which the oostegites were only just beginning to appear, there were 

 sternal processes precisely as in bidigitata and brevirostris. There was no trace of them in more mature 

 females. I have therefore added this character to the definition of the genus which should be revised 

 as follows: Carapace of moderate size with anterior margin produced into a triangular rostrum of 

 greatly varying length; antennal scale long, with the terminal spine of the outer margin extending 

 beyond the truncate apex; one or two spines on the outer distal angle of the sympod; eyeplates 



