BARGMANNIA REVISION 



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Fig. 4 Bracts of Bargmannia elongata. Scale bar = 1 mm. 



This thickening diminishes in the region of the thrust block, but there 

 is still a shallow median gutter that enfolds the nectosomal stem in 

 the region of attachment of the nectophore (Figure 2 B). 



In the preserved nectophores, the nectosac is a dorso-ventrally 

 undulating tube (Figure 2B, n; 2C), with prominent dorso-lateral 

 extensions in the mid region, and ventro-lateral ones both apically 

 and basally. However, this arrangement is not apparent in the 

 nectophores of the living animal (Figure 1 ).The nectosac is broadest 

 at about two-thirds its length, narrowing slightly towards its apex. It 

 has a distinct apical emargination; U-shaped in the younger 

 nectophores (Figure 3 A). Typically, the ventral, adaxial region 

 towards the apex of the nectosac is distinctly undercut and, from a 

 level just basal to the point of insertion of the pedicular canal, its wall 

 is devoid of musculature (Figure 2 B). The musculature of the 

 remainder of the nectosac appears well developed and gives it a 



distinctly opaque appearance. The ostium, in the preserved material, 

 opens onto the dorso-basal (abaxial) surface (Figure 2C, o) and is 

 roughly rhomboidal in shape. However, this probably is distortion 

 due to preservation (see Figure 1). In the Alvin specimens it has a 

 large velum, with a relatively small central opening, but in net 

 collected material often the velum is destroyed. The lateral walls of 

 the ostium extend out to form lateral processes (Figure 3C) that, 

 typically, are covered by patches of ectodermal cells of varied size. 

 Further such patches are present on the ventral margin of the velum, 

 but not on the dorsal margin, except for the youngest nectophores. 

 Some, if not all, of these cells probably produce bioluminescent 

 material since this has been found to be the case in another 

 Bargmannia spp. (Dr S. Haddock, personal communication). 



The long pallial canal (Figure 2B, pc) extends up into the median 

 thrust block, where it ends with a short dorsal inflection into the 



