124 PROCEEDINGS OF THE ACADEMY OF [1879. 



rior margin of the genital mass; its first part about 15.0 mm. 

 long with a diameter of about 1.0 mm., yellowish, passing through 

 a slight stricture into the second, which has only half the length 

 and half the diameter and is of a paler color. The penis nearly 

 4.0 mm. long, and 1.5 mm. in diameter. The glans in the upper 

 end of the cavity having a length of nearlj- 1.0 mm. (fig. 17); 

 the cuticula clothing the inside of it seemed to present hooks 

 similar to those in the typical species, but fewer and thinner (fig. 

 18). The spermatotheca spherical, about 3.0 mm. in diameter; 

 its duet as usual. The spermato-cysts spherical, about 1.6 mm. 

 in diameter. The ducts as usual, the cavity filled with sperma. 

 The mucus gland large, whitish, and yellowish-white; on the an- 

 terior part of the left side was a 3-olk-yellow mass, the large 

 cavity empty. The spoon-shaped lobe in the vestibulum had a 

 length of nearly 2.0 mm. 



Since the above observations were made two other individuals 

 of the same species have come under my notice. They were 

 obtained by Dall in September, 1872, at Coal Harbor, Shumagin 

 Islands, Alaska, on a muddy beach at low water. The color of 

 the living animal was "bluish." 



The specimens in spirits were 8.0 and 14.0 mm. long, 6.0 and 

 10.0 mm. broad, 3.5 and 5.0 mm. high respectively, and of yellow- 

 ish color. The form as above. 



The opening of the retracted gill transversely oval, as above 

 mentioned, the gill with 8-9 leaves. The anal papilla as above. 

 Both specimens were dissected. 



The central nervous system, the eyes, the oto-cysts, and the skin 

 quite as above mentioned. The oral tube about 1.5 mm. long. 

 The bulbus pharyngeus in the largest individual about 1.75 mm. 

 long, and 1.5 mm. broad and high. The sheath of the radula rather 

 prominent, bent upwards. The mouth-slit triangular; the lip- 

 plates chocolate-brown in the larger, yellow in the smaller indi- 

 vidual ; the structure as usual. The hooks in general a little 

 thicker at the point. The tongue with twent\'-seven te thirty 

 rows of plates ; further backwards thirty-six to thirty-nine freshly 

 developed and four immature rows; the total number of rows 

 was sixtj'-seven to seventy-three rows. In the posterior rows of 

 the tongue twenty-seven to thirty plates. The plates as previ- 

 ously mentioned; the median tooth (lig. 9) merely broader in the 

 hind part of the basal plate 



