650 R. C. PUNNETT. 
maldivensis procured was only 80mm. long. Maldivensis is also a more stunted form, its 
total length averaging about 18 times the collar length as against 23 times in laccadivensis. 
All of which considerations point to the fact that we are here dealing with two distinct 
though closely related forms. 
Ptychodera flava, var. saxicola (Pl. XXXVIII. fig. 17; Pl. XXXIX. figs. 28, 30, 31; 
Pl. XLIV. figs. 33—41). 
Locaity, ETc. Hulule, Maldive Is. Four specimens were obtained by breaking up a 
dead coral mass on the sand-flat. 
EXTERNAL FEATURES. This is a relatively short stunted form. The length of the 
smallest specimen when preserved was 32 mm., that of the largest 65 mm. The animal is 
thick in comparison with its length (Pl. XXXVIII. fig. 17). The total length relative to 
the collar as unity in the four specimens is 16:2, 12°8, 165, 163, giving an average of 
rather less than 16, which is low in comparison with such forms as laccadivensis (see p. 664). 
The genital pleurae are large but the liver saccules are small and not lobulated. Neither 
is there any differentiation into an anterior darker and a posterior lighter group. 
INTERNAL STRUCTURE. 
Proboscis. The radial arrangement of the longitudinal muscles is almost as well-marked 
as in laccadivensis. The proboscis cavity is fairly spacious. Dorso-ventral muscles in front 
of the pericardium may or may not be present. The ventral proboscis septum reaches 
nearly to the tip of the stomochord. The dorsal muscular decussation in the anterior part 
of the proboscis is well-marked and a few ventral fibres may pass from it round the cavity 
of the proboscis. Paired proboscis pores are present of which one or both may be in 
functional communication with the dorsal coelom. The racemose organ is well-marked but 
differs considerably in size among the different specimens. It may shew a certain amount 
of lobulation. 
Collar. The cavity of the anterior part of the collar is spacious. The dorsal collar 
septum in two cases shewed the usual condition, ze. was complete after the Ist root. In 
one case, however, it commenced about ‘5 mm. behind the Ist root, and in another a little 
in front of it. The ventral collar septum is more marked than usual, being in three of 
the four specimens complete in the hinder part of the collar. 
The nerve cord may shew a lumen continuous throughout or there may be a greater 
or less amount of occlusion. The number of dorsal roots varies from 2—4, In one specimen 
a somewhat remarkable dorsal root occurred. It was of considerably larger size than usual 
(Pl. XXXIX. fig. 28) and was obviously formed by two distinct portions, viz. an outgrowth 
from the collar cord with a cap of yellowish brown pigment, and an epidermal ingrowth 
at the end of which was a large mass of mucus. The two portions of the root fused more 
or less with one another. It is possible to regard such a structure as possessing some 
sensory significance, and to suggest that the mucous portion of the epidermal ingrowth may 
act as a crude lens in focussing rays of light on the pigmented portion of dorsal outgrowth 
from the collar cord. 
The cornua of the nuchal skeleton vary greatly in length but are on the whole un- 
usually short. 
Trunk. One of the most conspicuous features of this variety is the small size of the 
branchial region. Not only is the branchial portion of the cesophagus very small compared 
