ANELASMA SQTJALICOLA. 177 



There is a small interspace as usual between the first and 

 second pair of cirri. Internally, the cirri are occupied, 

 even up to their tips, by delicate striae-less muscles. 

 The external membrane of the thorax and limbs, when 

 examined under a very high power, is seen to be covered 

 with minute toothed scales, as in most Cirripedes. 



The thorax is articulated as usual : the posterior part, 

 however, is smaller, and tapers more suddenly than in 

 other species, and this corresponds with the smaller 

 size and more rudimentary condition, of the three pos- 

 terior pair of cirri, compared with the anterior pair. 

 The prosoma is hardly at all developed. The orifice 

 (PI. IV, fig. 2 e) of the acoustic (?) sack, beneath the first 

 cirrus, is unusually large. 



There are no filamentary appendages. 



Alimentary Canal. — The membrane lining the oeso- 

 phagus is unusually thin : it is furnished with the ordinary 

 constrictor muscles, and others radiating from them like 

 spokes of a wheel. The stomach is lined by unusually 

 prominent biliary folds, which in the duodenum are trans- 

 verse, sending forth, however, short folds at right angles ; 

 and these latter, in the proper stomach, become so much 

 developed that the folds appear longitudinal. The rectum 

 extends inwards, about as far as the base of the fourth 

 pair of cirri, but is very short, owing to the little develop- 

 ment of the three posterior segments of the thorax. 

 The anus is seated in its usual place, at the dorsal 

 basis of the penis, and is hidden by loose folds of skin ; 

 but there are no distinct caudal appendages. The stomach, 

 in the specimen examined, was quite empty. 



Reproductive Organs. — The penis (fig. 2, c) is thick, 

 short (about twice as long as the sixth cirrus), constricted 

 at the base, ringed, spineless, with the terminal aperture 

 large ; internally it is well furnished with muscles. The 

 two vesiculae seminales, appeared to be unusually small ; 

 and one was much smaller than the other ; they do not 

 (I believe) become united into a common tube, till near 

 the apex of the penis. They were empty ; and, I presume, 



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