102 PROCEEDINGS OF THE ACADEMY OF [1880. 



number of sei'ies here smaller, about five to eight. The spermatotheca 

 whitish, forming an oval bag of 3.0 mm. largest diameter ; the sperma- 

 tocysta yellowish, of 1.3-1.5 mm. largest diameter, the ducts as in the 

 typical Ac. pilosa. The chief duct, too, very (about 25.0 mm.) long, 

 rolled up in many coils, partly spiral, the diameter varying between about 

 0.3 and 0.15 mm. ; the last fourth of the duct (vagina) with scattered 

 black pigment, somewhat narrower and with a rather strong retractor 

 muscle at its commencement ; the interior of this duct with some few 

 strong longitudinal folds, clothed with a cuticula, and under the same a 

 very fine layer of round and angulated cells with a large round or oval 

 nucleus of the diameter of about 0.4 mm. and a rather large yellow 

 nucleolus (PI. X, fig." 13). In the cavity of the vagina more or less 

 sperma.i The mucous gland yellowish and white ; the central mass 

 (albuminous gland) yellow ; the duct with scattered black pigment on 

 the outside (also on the outside of the lower part of the penis), with 

 the usual fold. The vestibulum genitale with black pigment on the 

 folds, the same pignaent was seen in the lowest part of the cavity of 

 the penis and of the vagina and on the folds of the duct of the mucous 

 gland. 



A very similar animal, but " with brown mantle,'' was dredged by 

 Dall in Kyska Harbor (Aleutians) in July, 1873, on sand, at a depth 

 of nine to fourteen fathoms. 



It was of large size ; the length 21.0 mm., by a breadth of 11.0 and 

 a height of 9.0 mm. ; the margin of the mantle 2.0 mm. broad, the foot 

 6.0 mm. broad ; the height of the rhinophoria and of the gill 3 mm. ; 

 the genital aperture 3.0 mm. broad. The color dirty brown on the 

 upper side ; the rhinophoria and the branchial leaves yellowish, dotted 

 with grayish, especially on the stalk of the rhinophoria ; the sole of 

 the foot yellowish, the under side of the animal whitish ; the under 

 side everywhere with an enormous quantity of gray and black dots. 

 The number of branchial leaves nine. 



The peritoneum black-brown ; the central nervous system, eyes, 

 otocysts, as previously described. The bulbus pharyngeus of the 

 length of 4.5 mm. by a breadth of 3.0 and a height (with the crop) 

 of 4-T5 mm. ; the sheath of the radula projecting 1.25 mm. ; the crop 

 alone of the height of 2.3 mm. and 3.25 mm. broad. The lip-disk as 

 above, the thickenings in the lowest part of the mouth 1.2 mm. long, 

 of which nearly half freely projected. On the tongue nine rows of 



' The length of the spermatoduct and the duct of the spermatotheca 

 (vagina) was much more considerable than in the typical form. 



