BARGMANNIA REVISION 



67 



the nectophore. In the region where the infra-laterals leave the 

 ventral margins of the ventro-lateral wings, the latter begins to 

 thicken toward the mid-line. These thickened, rounded, unridged 

 lateral walls continue up to the apex of the nectophore and, on the 

 thrust block, delimit a narrow gutter that enfolds the nectosomal 

 stem (Figures 13B, 14A). 



The nectosac is a relatively short and narrow tube without any 

 marked dorso- ventral undulations (Figures 13, 14) in the preserved 

 specimens. Its apex lies approximately on a level with the 'shoulder' 

 of the nectophore. The nectosac occupies only c. 38% of the width 

 of the nectophore, as measured across its 'shoulder'. This results 

 from the fact that the extensive ventro-lateral wings not only increase 

 the depth of the nectophore, but also increase its relative width. The 

 apex of the nectosac is squarely truncate, without any marked 

 indentation. Its adaxial surface is distinctly undercut and, typically, 

 is devoid of musculature. The remaining musculature on the nectosac 

 appears much less dense in comparison with that of B. elongata. 



The canal system follows the basic Bargmannia plan. The long 

 pallial canal ends, apically. with a short dorsad inflection into the 

 mesogloea. On the nectosac the pedicular canal gives rise to only the 

 dorsal and ventral radial canals. In contrast to B. elongata and B. 

 amoena, in the preserved material the lateral radial canals have 

 straight courses down the lateral margins of the nectosac. However, 



in life, their courses appeared to be slightly undulating (Figure 12). 

 In the original colour photograph there are indications that the 

 pallial, dorsal, ventral, ostial ring, and proximal parts of the lateral 

 canals were suffused with a light orange-red colour. 



The ostial opening, in the preserved nectophores, typically is 

 displaced slightly dorsad and has a well-developed velum, but no 

 pronounced lateral processes. There are no marked patches of 

 ectodermal cells, although some nectophores show a single row 

 around the basal half of the ostium and/or a short, narrow band of 

 small cells that lies just dorsal to the outer branch of the apico-lateral 

 ridge. These cells, again, are presumed to be sites of biolumines- 

 cence. 



Bract (Figure 1 6). Only seven bracts were retained with the Alvin 

 material. However, because of their very characteristic shape, sev- 

 eral more have been identified from recent Discovery material. The 

 bracts measured from 1 3.5 to 27 mm in length and were remarkably 

 robust. They had a convex dorsal and a concave ventral surface. In 

 the Alvin specimen, there were two types of bract, with one type 

 being represented by only a single small bract. The key feature that 

 distinguishes them is the presence of only a single lateral tooth on 

 the outer margin (Figure 16A, B) of the larger ones; while the 

 smaller one has lateral processes on both sides (Figure 16C). The 



Fig. 16 Bracts of Bargmannia lata collected during DSRV Alvin Dive 966. Scale bar = 2 mm. 



