60 



P.R. PUGH 



1.86 mm; mean width 6.71 ± 0.88 mm; and the ratio of the overall 

 length to that of the nectosac averaged 1.42 ± 0.06. Finally six 

 specimens had even larger nectophores and were sexually mature. 

 They averaged 13.5 nectophores, whose mean length was 20.94 ± 

 2.36 mm; mean width 10.58 ±2.18 mm; and the ratio of the overall 

 length to that of the nectosac averaged 1.44 ± 0.05. 



As was the case forB. elongata, the apex of the thrust block of the 

 smaller specimens was drawn out to form a small digitiform process 

 (Figure 8A). In the larger specimens, this process usually became 

 folded over onto the ventral side of the nectophore (Figure 7C), so 

 that, in upper view, the thrust block appeared roundly truncate 

 (Figure 7A). 



The apico-lateral ridges are, in their preserved state, smoothly 

 curved and have no pronounced bend or side branches (Figures 7 

 & 8), as was found for B. elongata. After these ridges divide, the 

 inner branches extend obliquely down to reach the ostium; while 

 the outer branches curve down the sides of the nectophore, but 

 peter out well above ostial level. The latter is particularly marked 

 on the smaller nectophores (Figure 8C). 



Basal extensions of the meso-lateral ridges form the baso-lateral 

 margins of the mouth-plate (Figures 7 & 8). The structure of the 

 mouth-plate varies with the size of the mature nectophore. In the 

 smallest specimens, the mouth-plate is only slightly truncate basally 

 (Figure 8A). In the middle size range of specimens, the mouth-plate 

 becomes more and more emarginate and, in the largest ones, it has a 

 narrow U-shaped median indentation stretching up to the ostium 

 (Figure 7A). The mouth-plates of the immature nectophores of all 

 sizes of specimens show the same features as the corresponding 

 mature ones (Figure 9). 



Above the mouth-plate, in the small and medium sized speci- 

 mens, the basal extensions of the meso-lateral ridges curve slightly 

 in toward the mid-line (Figure 8B), before curving out again to form 

 the meso-laterals proper. In addition the infra-laterals do not unite 

 with the latter. On the largest specimens, there is no inward curve of 

 the meso-laterals (Figures 7B, 9B), but the infra-laterals have a very 

 weak connection with them (Figure 7B); However, the apical junc- 

 tion of the meso-laterals with the other ridges is always clearly 

 defined. The arrangement of the infra-lateral ridges, in the small 

 (Figure 8C) and medium sized specimens, is very similar to that 

 described for B. elongata. However, in the largest specimens, the 

 ventro-lateral wings are more extensive in the region where the 

 infra-laterals curve up to join the other ridges. The ventral margins of 

 these wings are distinctly emarginate. 



The nectosac, in its preserved state, appears as a dorso-ventrally 

 undulating tube; but this is probably a preservation artefact. The 

 dorso-lateral extensions, in the mid region of the nectosac, are 

 slightly more extensive than in B. elongata. At its apex the nectosac 

 has a shallow U-shaped indentation, and the adaxial wall is distinctly 

 undercut and devoid of musculature. On the remainder of the 

 nectosac the musculature appears much less dense that oiB. elongata, 

 and the nectosac is considerably more translucent. The arrangement 

 of the pallial and pedicular canals, and the radial canals on the 

 nectosac is similar to that of B. elongata. 



In the preserved specimens, the ostium opens almost basally and 

 has a large velum. Its lateral walls are only slightly extended to form 

 small lateral processes. The pattern of the patches of ectodermal 

 cells is similar to that of B. elongata, but the cells are more uniform 

 in size, and the patches more diffuse laterally. In addition, there are 

 two ventro-lateral patches of deeply granulated cells that are rela- 

 tively large and almost spherical. 



The youngest nectophores (Figure 9) typically show the absence 

 of a median thrust block The inner branches of the apico-lateral 

 ridges reach the ostium. The degree of emargination of the apex of 



Fig. 9 Bargmannia amoena sp. nov. A. Upper, B. lower, and C. lateral 

 views of young nectophore from specimen collected during JSL II Dive 

 1449. Scale bar = 2 mm. 



the nectosac is variable, according to the developmental stage. It 

 ranges from a narrow, median U-shaped indentation to a marked 

 emargination across most of the width of the nectosac. As noted 

 above the shape of the mouth-plate varies according to the size of the 

 specimen. On either side of the ostium there is a tract of small 

 ectodermal cells extending up toward the end of the outer branch of 

 the apico-lateral ridges. These tracts are longer than those seen on 

 the young nectophores of B. elongata and, again, are difficult to 

 discern on the adult nectophores. 



Bract (Figure 10). There are three pairs of bracts per cormidium. 

 Each is thin and leaf-like, with a slight thickening in the central 

 region of the proximal half. The dorsal surface is slightly convex, 

 and the ventral one slightly concave. In general their size is in 

 proportion with that of the nectophores, with those of the largest 

 specimens measuring up to 18 mm in length. No patches of ectoder- 

 mal cells were observed. However, in each cormidium, each 

 successive pair of bracts tends to be slightly larger than the pair 

 proximal to it. The proximal part of each bract is slightly asymmetri- 

 cal to allow for insertion onto the stem. The bracteal canal extends to 

 about two-thirds to four-fifths the length of the bract. It remains in 

 close contact with the ventral wall of the bract at all times. 



There is much variation in the shape and form of the bracts, but 

 two basic types can be distinguished; both having two pairs of lateral 

 teeth. In one type, which make up the first two pairs of bracts in each 

 cormidium, the bracts are relatively symmetrical. The more distal 

 pair of lateral teeth are very variable in shape, ranging from being 

 virtually absent to being quite marked (Figure 10A, B, D). In the 

 second type (Figure 10C, E), which are the distal pair, the bracts are 

 asymmetrical, and the bracteal canal can have a distinct proximal 

 curve. The distal pair of lateral teeth are well developed and closer 



