8 SALPID^. 



terminating in two long conical processes (^p.p.^ with a coecum of 

 the respiratory cavity (c. c.) at the base (Fig. 1). When seen in 

 profile (Fig. 3), it is trimcated abruptly at the two ends, from the 

 ventral to the dorsal side ; the extremities are slightly convex ; the 

 posterior truncating plane is more inclined than the anterior, and 

 as the dorsal side is at the same time somewhat convex, this gives 

 the anterior end a slightly pointed appearance. Besides the two 

 large posterior conical processes, there are two sharp lateral ones, 

 quite small (I. p.'), and seen only from the ventral side (Fig. 2) on 

 each side of the termination of the respiratory cavity, and two other 

 short processes (p.p.^ situated on the median line (Fig. 2) at the 

 posterior extremity of the body, placed one above the other (Figs. 

 1 and 3). The larger process is situated nearest the posterior open- 

 ing. These processes, like the surface of the body, are quite smooth. 

 There are six muscular bands entirely encircling the body ; the sec- 

 ond, third, and fourth (beginning at the anterior extremity) unite 

 on the ventral side, while on the dorsal side the muscular bands are 

 nearly equidistant (see Fig. 1). The anterior opening for the ad- 

 mission of water is by far the largest of the two openings of the 

 respiratory cavity ; it occupies the whole width of the body (Figs. 

 1, 2), while the posterior one, through which the water is expelled, 

 is much narrower and placed at a short distance from the posterior 

 extremity, at the base of the truncating plane, on the ventral side, 

 the anterior opening (a.) being nearer the dorsal side. The lips 

 which close these openings are quite prominent, and can l^e thrown 

 out considerably beyond the general outline, either when drawing 

 in water or forcing it out ; the lips of the anterior aperture open 

 dorsally, those of the other end open in the opposite direction (6.) 

 when in action (Fig. 3). 



The external and internal tunics are well defined ; hollowed out 

 from this internal tunic arise the circulating veins ; the larger ones 

 are especially apparent at the point where the muscular bands are 

 imbedded in this tunic. The gill {g.^ runs nearly parallel with 

 the ventral surface in the shape of a thick, hollow column, wider at 

 the posterior extremity ; it communicates dorsally and vcntrally 

 with the circulating system, and is strongly ribbed on the back and 

 sides with bands of cilia. At the anterior edge of this gill is placed 

 the languet (/.), a long, grooved, conical process slightly 5-shaped, 

 extending to the dorsal side of the respiratory cavity and hanging 

 freely within it, attached by a broad base to the ventral side of the 

 cavity ; the base of attachment is formed by a widening of the foot 



