Messrs. Hancock and Embleton on the Anatomy of Eolis. 9 



orifice of the month. The circular fibres are to be traced from 

 end to end of this tube^ but are most abundant at its posterior 

 part, where they form a strong belt or sphincter, PI. I. figs. 4/ 

 and 6 k. The use of the outer lips appears to be chiefly confined 

 to sensation, for they are abundantly supplied with nerves, and 

 are retracted by means of their straight fibres when the animal 

 takes its prey. 



From the circular belt at the base of the outer lips pass back- 

 wards series of fibres, PL I. fig. 4i g g, the strongest and longest 

 of which are below, corresponding to the foot. These fibres are 

 inserted into the fleshy foot and into the common integument of 

 the sides and top of the body, to which they attach the whole 

 buccal mass, and their office is to retract that mass : this they will 

 do most efficiently when the foot has firm hold of the ground. 



From the same belt are seen passing backwards and lying 

 against the external surface of the corneous plates, flat, shining, 

 semitransparent bands of muscle, PI. I. figs. 4^, 7 b, and PI. II. 3^, 

 which unite and divide irregularly as they are continued to their 

 insertions along the upper and posterior borders of the horny 

 plates. These bands appear to be antagonists to the last-men- 

 tioned, and may advance and rotate the buccal mass, during the 

 prehension and cutting of the prey, and probably may assist in 

 retracting the outer lip. 



The general characters and the muscular arrangement of the 

 buccal mass do not appear to vary materially throughout the ge- 

 nus Eolis. [See that of E. coronata, PI. II. fig. 3.] The lips are 

 nearly the same in all. There are corneous plates and spiny 

 tongue in all. In E. coronata however, PI. II. figs. 6 and 8, 

 the jaws are slightly modified in form. The tongue also varies, 

 and is composed of a single longittidinal row of large, strong, re- 

 curved spines or teeth which are minutely pectinated on each 

 side. 



In E. nana the same compound tooth is found, PI. II. fig. 10 

 and PL III. fig. 3. 



In E. alba the tongue is composed of a single longitudinal row 

 of twenty large, simple, recurved spines, PL II. figs. II and 13, 

 and in E. olivacea there are between fifty and sixty transverse rows, 

 each containing about twelve stoutish, almost straight spines, 

 PL II. figs. 13 and 14. 



The spines of these tongues are very minute, and in E. papiU 

 losa are not more than one-sixth the thickness of the ordinary 

 hair of the human head. They were often observed to be broken 

 ofi" abruptly, but never bent or partially fractured ; hence we were 

 led to suppose that they were not composed of horny tissue, and 

 were induced to try the efiect of some reagents upon them. 

 Neither acetic nor nitric acids produced any change in them, but 



