190 IBLA CUMINGII, 



margin under the cirri, and can be traced with difficulty 

 to the ventral margin. The thorax, itself rudimentary, 

 and supporting rudimentary cirri, is in some individuals, 

 as in the one represented (fig. 1, magnified 32 times), 

 covered by, or received in the oblique fold k, just men- 

 tioned : in other individuals the thorax is drawn out. and 

 then the fold shows merely as a notch on the dorsal margin, 

 and the basal articulations of the cirri stand some little way 

 above it. The basal edge of the large, well-developed 

 mouth can be traced all round, and on the ventral margin 

 (b), is generally marked by a slight notch. The dimen- 

 sions and proportions vary much : the longest specimen, 

 including the imbedded portion, was ^th, and the shortest 

 barely ^ths of an inch in length ; the width of the widest 

 portion varied from ^ ths of an inch : the specimen 

 figured (PI. IV, fig. Sa, and PI. V, fig. 1,) is a broad, 

 short individual. Generally, the middle of the peduncle 

 is rather wider than the upper part. 



Peduncle — The main part of the animal, as may be 

 seen in the drawing, consists of the peduncle, of which 

 the imbedded portion tapers more or less suddenly in a 

 very variable manner, and is of variable length, — in one 

 specimen being one fourth of the entire length, and in 

 another consisting of a mere minute blunt point. The 

 free upper part of the animal is bent in various directions, 

 in relation to the imbedded portion. The latter passes 

 obliquely through the chitine membrane and corium, 

 lining the sack of the female, and running along amidst 

 the under-lying muscles and inosculating fibrous tissue, 

 is attached to them by cement at the extremity. The 

 peduncle is often, but not in the individual represented, 

 much constricted at the point where it passes through 

 the skin of the female, and generally at several other 

 points, especially towards the extremity (see fig. 1) ; the 

 stages of its deeper and deeper imbedment being thus 

 marked. The constrictions are, I believe, simply due to the 

 continued growth of the male, whilst the hole through 

 the membrane of the female does not yield. The imbed- 



