ABYLA. 45 



Abyla Bassensis. pi. II, fig. 1. 



Diphyes Bassensis, Quoy and Gaimard, 1833. 

 Abyla quadrilalera, De Blainville, 1830. 

 Bassia quadrilalera, Quoy and Gaimard, 1824. 

 Calpe bassensis. Lesson, 1843. 

 Sphenoides (?), Huxley (infr^). 



The proximal nectocalyx has the same general form as in the foregoing species ; but, 

 whereas in the latter, the base of the quadrate process, which contains the lower portion of the 

 hydroecium, does not occupy half the inferior face of the organ, it here takes up a much 

 greater space, and is proportionally shorter and wider, its lower edges being somewhat 

 everted. The apex of the large and bell-shaped hydrcccium extends nearly to the middle of 

 the organ, and is fully as long as the nectosac, which is wider and shorter, and has a pro- 

 portionally narrower mouth. The nectocalycine duct passes to its posterior face rather above 

 its middle. The somatocyst is ovoid, and has no narrow cajcal prolongation. 



The distal nectocalyx is prismatic, and widest in the middle of its length. The prism 

 appears at first to have only four sides and as many longitudinal ridges, but in reality there are 

 five ; that in the middle of the convex posterior face being almost obsolete, and marked only 

 by a very small inferior pointed prolongation. 



The postero-lateral crests are somewhat stronger, and their inferior points more prominent, 

 and the antero-lateral ones are still more marked ; the right antero-lateral point is the 

 strongest. The anterior surface presents a deep longitudinal groove, bounded on each side 

 by the antero-lateral ridges. From the right-hand ridge a plate stretches transversely to the 

 left-hand one, and is fixed to the latter for the greater part of its length, but it ends inferiorly 

 in a free, convex, deeply serrated edge (fig. 1 a). Beneath this plate may be seen indications 

 of the existence of another, so that the anterior half of the hydroecial canal is probably formed 

 by the imion of two plates, one from each antero-lateral ridge. 



The inferior surface is truncated, and shelves downwards anteriorly into the septal ridge, 

 which connects the terminations of the two antero-lateral crests. 



The rounded aperture of the nectosac lies in the middle of the broad, flat inferior 

 surface, of which it occupies only a small portion. It is, as usual, surrounded by a membranous 

 valve, and leads into a large nectosac, which gradually widens, attaining its greatest dimen- 

 sions about the middle of the organ, and then narrowing again till it ends at about the junc- 

 tion of the upper with the next fifth of the long diameter of the organ. The posterior and 

 superior surface of the upper end shelves forwards and downwards, and where it joins the 

 anterior surface, is the point of division of the nectoduct, which ascends thence obliquely to 

 the floor of the hydroecial canal. 



The upper end of the distal nectocalyx is deeply notched, so as to present a sort of 

 articular surface, into which the solid angle of the proximal nectocalyx, formed by the junction 

 of the inferior and the posterior faces, is received. The posterior facet of the notch looks 

 forwards and upwards, and is formed by the upper face of that portion of the distal necto- 

 calyx which contains the nectosac. The lower half of the posterior face of the superior 

 nectocalyx rests upon it. 



