eae ee hy 
i 
q 
4 
; 
* 
: 
W. Lilljeborg on the Genera Peltogaster and Liriope. 169 
size of the parasites is in direct relation to that of the Paguri. 
On the smallest species of the genus Pagurus (P. chiracanthus), 
which is sometimes met with in shells as small as Cerithium 
reticulatum, the author has found specimens of Peltogaster micro- 
stoma only two millimetres in length. These contained no ova; 
but close to their organ of adhesion, which was but slightly 
developed, there were some long and fine filaments, apparently 
hollow canals, perhaps belonging to the cement-apparatus. 
Rathke also found similar filaments placed in two tubercles on 
the membrane of the “ digestive sac,” and probably in commu- 
nication with the parts described above as male organs. Per- 
haps these, as well as the female organs, assist in the production 
of cement. 
Besides Rathke’s P. Paguri, the author describes two new 
species. The following table gives the distinctive characters of 
the three :— 
PROMO fo 6 ors ena fs Paguri. 
Organum r 
adfigendi, sean 
Peltogaster ae < marginata.. suleatus. 
acetabulum oe 
pertura y, 
corporis 
_antica minima, 
neque 
\marginata.. microstoma. 
1. Peltogaster Paguri, Rathke. PI. IV. fig. 12. 
Diagn. Acetabulum in medio latere ventrali situm, ramosum.— 
Longit. maxim. cire. 16 millim. 
Peltogaster Paguri, Rathke, Reisebemerkungen, p. 105, tab. 6. figs. 12-16; 
Beitr. z. Fauna Norw. p. 245, tab. 12. fig. 17. 
This is the largest known species. It is subject to variations 
both in its form and in the structure of the envelope of the body ; 
even the structure of the organ of adhesion and of the aperture 
at the anterior extremity of the body varies to a certain extent. 
The form of the two individuals seen by the author is represented 
in Pl. IV. fig. 15. But these were small specimens, one mea- 
suring 8 and the other 4 millim. ; the latter contained ova, the 
former did not. The form is more clumsy than in the other 
species, and nearly cylindrical, with the anterior part much 
thicker than the posterior. The body is much curved in a direc- 
tion parallel to the curvature of the abdomen of the Pagurus ; 
the skin is smooth, except a few Jongitudinal and transverse 
folds ; it is generally thick and but slightly ira kes, especi- 
Ann. & Mag. N. Hist. Ser. 3. Vol. vi. 12 
