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 : — 



(Organum 

 adfigendi, 

 acetabulum 



ramosum Paguri. 



< 



simplex. 

 Apertura , 

 corporis 

 ^ antica 



magna, 

 marginata 



sulcatus. 



neque 

 l^marginata 



. microstoma. 



1. Peltogaster Paguri, Rathke. PI. IV. fig. 12. 



Diagn. Acetabulum in medio latere ventrali situm, ramosum. — 



Longit. maxim, circ. 16 millim. 

 Peltogaster Paguri, Rathke, Reisebemerkimgen, 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 PI. IV. fig. 1 b. 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 longitudinal and transverse 

 folds ; it is generally thick and but slightly transparent, especi- 



Ann.^ Mag. N. Hist. Ser. 3. Vol. vi. 12 



