68 



P.R.PUGH 



larger ones also were distinctly asymmetric proximally; and the 

 bracteal canal made a right-angled bend. These differences may be 

 just the result of growth, or may related to their point of attachment 

 on the cormidium, as was noted for B. amoena. Both types of bract 

 are distally truncate, and possess a semicircular dorsal ridge that 

 delimits a rounded distal facet. The ridge connects the tips of two 

 distal processes. 



The shape of the distal margin of the larger bracts varied consid- 

 erably. On some, the inner margin of one of the distal process 

 extended up the ventral side of the bract forming a flap-like struc- 

 ture; while on others this flap was absent. Another small ventral flap 

 can be present, approximately in the mid line, in the proximal half of 

 the bract. The bracteal canal lies just above the ventral surface of the 

 bract and ends close to its distal margin. The original colour photo- 

 graph of the Alvin dive 966 specimen indicated that, in life, some of 

 the bracteal canals had an orange-red pigmentation like that of the 

 remainder of the stem. 



GASTROZOOID and TENTACLE. Only a small portion of the proxi- 

 mal end of the siphosome was preserved from the Alvin specimen, so 

 that only a few young gastrozooids were present. These measured up 

 to 7 mm in length, and showed no distinguishing features. No 

 pigmentation is apparent in the preserved material, but in life they 

 had a deep red pigmentation. 



The tentacles attached to the gastrozooids mainly bore young 

 tentilla; with a c. 1 mm pedicel; a 2.5 mm cnidoband, apparently 

 devoid of large nematocysts; and a c. 4 mm uncoiled terminal 

 filament, apparently without a terminal process. However, a few 

 more mature tentilla had cnidobands extending to more than 8 mm, 

 with 4—6, possibly more, large nematocysts (stenoteles), arranged 

 biserially and arranged alternately, at their proximal ends. Small 

 nematocysts, possibly of two types, are present throughout the 

 cnidoband and terminal filament. 



SlPHOSOMAL TENTACLES AND BUDS. The peculiar tentacular proc- 

 esses, previously noted in specimens of B. elongata and B. amoena, 

 are present on the small part of the siphosomal stem remaining but, 

 because of the contracted state of the latter, it was not possible to 

 ascertain their exact disposition. They are narrow, delicate struc- 

 tures, measuring up to c. 4 mm in length, and are covered in large, 

 rounded ectodermal cells. Small nematocysts are present but, with- 

 out destroying the tentacle, it was no possible to assess whether they 

 had a biserial arrangement, as noted for the previously described 

 species. Siphosomal buds also appear to be present, but their arrange- 

 ment could not be discerned. 



GONOPHORE. A few loose male gonophores are present with the 

 Alvin material. They are identical to those previously described for 

 B. elongata and B. amoena. 



Distribution. A total of 288 nectophores and 27 bracts of fi. lata 

 have been found in recent Discovery collections (Table 1 ). The data 

 indicated that, in the North-east Atlantic Ocean, B. lata was more 

 commonly collected at lower latitudes and at deeper mesopelagic 

 depths; with a mean depth of c. 1000 m.Totton's material came from 

 two sites in the South Atlantic Ocean and one in the Gulf of Aden; the 

 Alvin material came from off San Diego, California, USA; and 

 Mapstone's (1998) from off British Columbia, Canada; thus indicat- 

 ing a widespread geographical distribution for this species. 



Remarks concerning the identification of Bargmannia lata. 

 B. lata can now be easily distinguished from other Bargmannia spp. 

 The nectophores are relatively broad, with extensive ventro-lateral 

 wings, that are markedly emarginate along their ventral margins. 

 The median thrust block is relatively long so that the ratio of the total 



length of the nectophore to that of the nectosac is high, c. 1.6, or 

 more for net collected material, as compared with c.1.31 in B. 

 elongata and c. 1.41-1 .44 in B. amoena. The nectosac appears as a 

 relatively short, narrow, straight-sided tube, without any pronounced 

 dorso-ventral undulations, and squarely truncate apically. It occu- 

 pies only c. 38% of the width of the nectophore, as compared with 

 45% in B. elongata. The large, robust bract, with a semicircular 

 dorsal ridge connecting the tips of the baso-lateral processes, also is 

 distinctive. 



Despite these differences it is clear that Totton (1954, 1965), had 

 little reason to suspect that he was dealing with at least two 

 Bargmannia spp., particularly as he had so few, poorly preserved 

 nectophores. However, with the collection of complete specimens of 

 Bargmannia spp. by submersibles the specific differences between 

 the various types of nectophore that Totton illustrated can now be 

 established. 



Bargmannia gigas sp. nov. 



Holotype. BMNH 1998.2166 one nectophore, preserved in 

 Steedman's solution, collected at Discovery St. 8560#2 (0°03.1'N, 

 22°44.2'W; 27-vii-1974; 1510-2000 m; RMT8 net). 



Paratypes. Three nectophores, preserved in Steedman's solu- 

 tion, from the same Discovery sample. BMNH 1998.2167-69. 



Material examined. The type and paratypes, and a further ten 

 nectophores from the same station, which are retained in {he Discov- 

 ery collections at the Southampton Oceanography Centre. All the 

 nectophores are presumed to have originated from a single speci- 

 men. 



Diagnosis. Nectophores relatively enormous, up to 52 mm in 

 length; with large ventro-lateral wings; with small mouth-plate 

 deeply divided. Basic ridge pattern supplemented by three pairs of 

 ridges, all dividing from apico-laterals; two pairs short, directed 

 toward mid-line; third pair directed laterally. Nectosac without 

 dorso-ventral undulations; apex only slightly emarginate; ostial 

 opening large. Ratio of overall length of nectophore to that of 

 nectosac averages 1.63. 



Description. Nectophores (Figures 17 and 18). The relatively 

 enormous nectophores varied in size from 14.5 x 8 mm (length x 

 width) for the smallest, immature one, to 52 x 20 mm, respectively, 

 for the largest The mean dimensions for the fully developed 

 nectophores were length: 41.0 ± 6.96 mm and width: 19.1 ± 2.52 

 mm, and the ratio of total length to that of the nectosac was 1 .63 ± 

 0.10. The nectophores, in their present state of preservation, are 

 devoid of pigmentation and, in most cases, the muscular lining of the 

 nectosac has become detached and/or lost. The large, thickened, 

 central thrust block is roundly truncate. 



The basic pattern of the prominent ridges conforms with that of 

 the genus, and both the inner and outer branches of the apico-laterals 

 appear to reach the dorso-lateral margins of the ostium. In addition 

 there are three pairs of ridges that branch from the apico-laterals 

 (Figures 17A, 1 8). Two of these pairs of ridges are very short and run 

 down into the shallow median gutter, towards the mid-line. One pair 

 arises at a level of about two-fifths the length of the nectosac, while 

 the other originates from the inner branches of the apico-laterals, 

 close to the ostium. The other pair arises from the outer branches of 

 the apico-laterals and extends up the sides of the nectophore between 

 the apico- and meso-laterals. These ridges peter out approximately 

 at the mid-length of the mature nectophore. Below them the lateral 

 walls of the nectophore often show prominent thickenings (Figure 

 17C). 



