THE ENTEROPNEUSTA. 653 
Trunk. The branchial region in this variety is very short, averaging only a quarter 
as much again as the collar length (see Table 12, p. 673). In the Maldive specimens 
the branchial part of the cesophagus is at least as large and generally somewhat larger 
than the ventral portion. In the Minikoi specimens on the other hand it is somewhat 
smaller, a feature in which they approximate to laccadivensis. The post-branchial groove is 
very short in the specimens from Hulule, not being more than about #, of the length of 
the short branchial region. In the Minikoi specimens it is rather longer. The genital 
pleurae are large in the branchial region (Pl. XLVI. figs. 50, 54). They diminish in size 
considerably in the region of the post-branchial groove (Pl. XLVI. figs. 53, 55), after which 
they are very small. 
The proportions of the various regions of the body in the above account have been 
determined from an examination of 28 specimens from Hulule (vide Table 12, p. 673). 
Five specimens only were procured from Minikoi and, as will be seen in Table 4, Nos. 4 
and 5, these differ somewhat from the Hulule forms. It is possible that examination of a 
larger amount of material may shew that these Minikoi specimens belong to a distinct variety. 
The difference in their mode of occurrence (p. 651) would seem to point the same way, 
but in any case they are very closely related to the Hulule form. 
Ptychodera flava, var. muscula (Pl. XLII. fig. 18). 
Locauity, ETc. A Maldive form from Goifurfehendu Atoll, Goidu. It was obtained from 
the sandy shore to the east of the island in the sand below the weed and under some 
square slabs of beach sandstone. In company with it was found Spengelia porosa. About 
a dozen specimens procured in all. 
EXTERNAL FEATURES. Colour in life pale yellow with very black hepatic region. A 
small form with a total length after preservation of 31—48 mm. Average length compared 
with collar as unity = 156. A somewhat short and stoutly built form, generally speaking. 
The anterior hepatic caeca are, after preservation, darker than the rest. 
INTERNAL STRUCTURE. 
Proboscis. The internal longitudinal musculature is very strongly developed and closely 
surrounds the central complex, almost obliterating the proboscis cavity. No dorso-ventral 
muscles anterior to the pericardium. The ventral proboscis septum is short and does not 
reach nearly to the tip of the stomochord. Of the paired proboscis pores one may not 
be functional. The racemose organ may be small or fairly well marked and slightly lobulated. 
The nuchal skeleton has a well-developed keel which gives off a flattened expansion over 
the racemose organ. Such an expansion occurs generally in the genus but is not usually 
so well-marked as in the present variety (Pl. XLII. fig. 18). A strong dorsal muscular 
decussation occurs in the anterior portion of the proboscis, and from it pass some circular 
fibres ventrally. 
Collar. The musculature of this region also isewell developed. The cavity in the 
anterior part of the proboscis is comparatively large. The dorsal septum is found as usual 
after the first root though it may not immediately be complete. The ventral septum is 
absent or traces of it only are to be found. 
The lumen of the nerve cord shews a marked tendency to become occluded. Three or 
four dorsal roots may be present. 
Gan. 84 
