BARGMANNIA REVISION 



65 



Fig. 13 Bargmannia lata. A. Upper, B. lower, and C. lateral views of mature nectophore collected during DSRV Alvin Dive 966. D. Ventral view of the 

 apex of another nectophore. Scale bar = 2 mm. 



is due to the fact that the base of the nectophore frequently is 

 damaged, resulting in an underestimate of both measurements, and 

 a consequent increase in their ratio. 



The central thrust block forms an extensive triangular process 

 whose apex is often roundly pointed Figure 13 A). However, on 

 several nectophores one side is drawn out to form a small digitiform 

 process that may be folded over laterally or ventrally (Figure 13D). 

 The ridge pattern conforms to the basic Bargmannia design, with no 

 extra ridges being present. 



From their junction with the meso- and infra-lateral ridges on the 

 'shoulder' of the nectophore, the apico-laterals are directed ob- 

 liquely toward the mid-line. They closely approach each other, and 

 continue for some distance in a basal direction; leaving a narrow 

 median furrow between them. At about one quarter the length of the 

 nectophore, in the Alvin material, they rapidly curve out laterally, 

 before giving rise to the typical inner and outer branches (Figures 

 13-15). The inner branch curves obliquely toward the mid-line and 

 joins the ostium on its dorsal surface. The outer branch curves down 

 and then round and ends on the lateral margin of ostium, although it 

 can be difficult to discern basally. The angle between the apico- 

 lateral ridge and its inner branch is acute (Figure 13 A). However, in 



less well preserved nectophores, this pronounced angle is not always 

 apparent (Figure 14B) and the inner branch can appear as a simple 

 continuation of the main ridge. 



The mouth-plate is small and made up of two rounded lobes that 

 unite in the mid-line, slightly basal to the ostium. The ventro-lateral 

 margins of these lobes are, as usual, formed by basal extensions of 

 the meso-lateral ridges. Above the ostium, on the ventral surface of 

 the nectophore, these basal extensions curve round toward the mid- 

 line, before looping back out as the meso-laterals proper and 

 continuing apically. After a relatively long distance, in comparison 

 with B. elongata and B. amoena, the infra-laterals branch from them 

 (Figures 13C, 15C). The meso-laterals then continue obliquely up 

 and across the lateral margins of the nectophore to join the apico- 

 and infra-laterals on the 'shoulder' of the nectophore. The junctions 

 with the other ridges, both apically and basally, are obvious, unlike 

 in B. elongata. 



In the basal two-thirds of the nectophore, the infra-lateral ridges 

 form the ventral margins to the ventro-lateral wings (Figure 13C, 

 15C). These wings are relatively large in comparison with those of 

 B. elongata and B. amoena, occupying more than half the depth of 

 the nectophore. They are distinctly emarginate in the mid region of 



