no DISCOVERY REPORTS 



' Discovery II ' took 144 well-preserved anterior nectophores of various sizes, together with a similar 

 number of posterior ones on 1 1 November 1 95 1 at Station 2905 in the Red Sea. Fifty-five are bidentate, 

 and twenty-eight are of the extreme quadridentate form. Fifty-eight others have a pair of lateral teeth 

 of various lengths (which I am unable to record at the moment). In my opinion they bridge the gap 

 between the two forms satisfactorily. Three have no teeth at all but resemble this species more than 

 they do S. chuni. My conclusions are that (1) it is not a question of the number of teeth but of the 

 total development of the ' denticulate character '. For in bidentate forms the two teeth may be quite 

 small, whilst in the four-dentate form they never are; and the inner distal corners of the mouth-plate 

 of the bidentate form are generally rounded and not denticulate, whilst in the four-dentate form they 

 are always denticulate, so that there is a gradual change from the condition where only two dorsal teeth 

 are present and the mouth-plates are rounded, to the extreme four-dentate form with long dorsal 

 and lateral teeth and 'denticulate' mouth-plates; (2) only one species is to be recognized. The name 

 quadrivalvis has priority. It is possible that a genetical explanation of the variability in number and 

 size of these periostial teeth might be found in a chromosomal deletion or in a preponderance of a 

 suppressor gene. Fortunately this species is fairly abundant at times in the Mediterranean, and also 

 in Valencia Harbour, Ireland, at either of which places genetical experiments might be tried in order 

 to confirm the view that only one species is represented. S. quadrivalvis would then be established 

 as one species of siphonophore whose characters were not so clear cut as most others. 



Lensia Totton, 1941 

 Since writing on the species of Lensia in 1941, I have repeatedly found specimens of them all, 

 including Leloup's interesting little L. meteori, which I had not at that time seen. My grouping into 

 species appears to be sound in the light of twelve years' further work, and only three further new 

 species have appeared. Nineteen of the twenty-one known species are found in the Indian Ocean, 

 two having been previously recorded there. I have figured fourteen of these before (1932, 1941). 

 Bigelow & Sears (1937) figured L. conoidea, L. fozvleri and L. multicristata; and Leloup (1934a) 

 figured L. meteori. My present identifications are in accordance with these figures and related 

 descriptions. 



Lensia hotspur Totton, 1941. 



The syn types from ' Discovery ' Station 100 exhibited a very small hydroecial cavity which included 

 the base of the somatocyst. In the Red Sea specimens the base of the somatocyst generally projects 

 down slightly below the baso-lateral margins (Text-fig. 54C-E). At 'Manihine' Aqaba Station 13 

 (135-0 m.) four well preserved anterior nectophores, between 4-0 and 4-5 mm. in length, were taken. 

 Two of them are of this same type, and two of the type in which the base of the somatocyst does not 

 extend below the baso-lateral margin. From 'Manihine' Red Sea Station 8 came 19 anterior necto- 

 phores containing both types and intermediates in which the base of the somatocyst is on a level with 

 the baso-ventral margin. Associated with anterior nectophores from the Gulf of Aqaba were posterior 

 nectophores and eudoxids, which unfortunately cannot be described and figured at the present time, 

 except to say that the mouth-plate of the posterior nectophore has a rounded notch in its distal edge, 

 and that the upper end of the left ventral ridge is not square but angular. Specimens of this species 

 though abundant are nearly always in a poor condition. But systematists in future would do well to 

 watch for variation in this respect, and to make certain that we are not dealing with more than one 

 species. It is certainly clear now that the 'Carnegie' specimen drawn by me (1941, fig- 13) belongs 

 to a different species, which has since been taken abundantly by H.M.S. ' Challenger ' in the E. Tropical 

 Pacific in October 1950. The new species I have named in honour of the ship. L. hotspur occurs side 



