F. M. Turnhull — Anatomy and Habits of Nereis virens;. 273 



Whoii the proboscis is iiisido the body, it takes the position sliown 

 in tiniires 16 and 20, tlie cesojthagus being curved and pushed back 

 against the intestine ; but when it is forced out, the oesophagus 

 straightens, and that part of the proboscis which is protruded takes 

 the position shown in figures 1 7 and 1 8, these figures sliowing the ar- 

 rangement of the jaws and denticles, figure 17 giving the dorsal 

 view and figure 18 the ventral view; the buccal ring is very much 

 stretched ; and the head, antenna^ and tentacular cirri are forced over 

 on the back (fig. 17). The jaws are imbedded in and attached to 

 the special muscles, in such a manner that the more the proboscis is 

 l^rotrudcd the farther apart their points move, and when the probos- 

 cis is withdrawn they close like a pair of scissors, their points crossing. 

 The jaws (fig. 19) are curved like hooks, and have their inner concave 

 edge denticulated with about ten teeth. They and the denticles are 

 composed of a black chitinous material. The denticles, which are 

 conical and pointed, are not attached to muscles, but are simply im- 

 bedded in the surface. The number and size- of the denticles, and 

 even their positions, vary considerably in the different specimens ex- 

 amined. T think it would be hard to fi.nd two specimens exactly alike 

 in this respect. Among seven worms, I found five with one denticle, 

 one with two denticles, and one with seven denticles on the median 

 anterior area of the dorsal side (fig. 17, o). 



Among six worms, I found two with two denticles and four with 

 none at all on the posterior median area of the dorsal side (fig. 17, t). 

 On the left submedian anterior area of the dorsal side (fig. 17, I), the 

 number of denticles varied from three to eight ; and on the right sub- 

 median anterior area of the dorsal side (fi:g. 17, I') from two to eight. 

 In only one case did the two last areas have the same number of den- 

 ticles. On the left submedian posterior area of the dorsal side (fig. 



17, s) the number of denticles varied from none to five; and on the 

 light submedian posterior area of the dorsal side (fig. 1 7, s') from 

 one to four. 



The denticles on the lateral and ventral posterior areas (fig. 17 and 



18, r) vai-y considerably in number, position and size. Among four 

 worms, the number of denticles on the right lateral anterior area (figs. 

 17 and 18, n) varied from twelve to twenty-five; and on the left lat- 

 eral anterior area (figs. 17 and 18, n') from eleven to thirty. 



Among five worms the number of denticles on the anterior median 

 area of the ventral side (fig. 18, y) varied from four to twelve. On 

 each of the two submedian * areas of the ventral side (fig. 18, x') 

 there was one denticle. 



Trans. Conn. Acad., Vol. III. 35 August, 1876. 



