GYMNOTOPLAX. 211 



two smaller and narrower posterior tentacles, which are flattened 

 and folded ; on the left side there is a conspicuous dark blue eye 

 behind the base of the dorsal tentacle, but on the right side the eye 

 is concealed or wanting in our specimen. The gill occupies the 

 groove below the mantle on the right side, and is nearly one-third 

 the length of the shell ; just in front of the gill there is a low 

 rounded prominence with a central orifice. The shell is thin, trans- 

 lucent, pale yellowish-white, oblong, with the sides nearly parallel 

 and the anterior end bluntly rounded. The spire is a little promi- 

 nent, terminal and strongly curved to the left, with the nucleus 

 smooth, glassy and incurved, situated at some distance from the 

 margin. The surface of the shell is covered with numerous strong, 

 irregular, concentric undulations, and by much smaller and finer 

 lines of growth, which are crossed by microscopic, interrupted, 

 radiating lines, giving a very finely reticulated appearance. Length 

 of the shell 13%5, breadth 8'5 mill. (Verrill). 



Off Martha's Vineyard, 250 fms. (U. S. Fish Comm.). 



Pleurobranchus americanus V., Trans. Conn. Acad., vi, p. 429, 

 pi. 44, f. 13 (April, 1885). 



G. MARTENSI Pilsbry, n. n. PI. 48, figs. 34, 35. 



Mantle deeply incised in front, projecting beyond the foot all 

 around, the margin thickened and somewhat ragged, evenly and 

 finely granose all over, yellowish-brown, with round spots of dark 

 purple-brown, much scattered, more numerous near the periphery 

 and at the circumference of the part of the mantle covering the shell. 

 Tentacles and angles of the head dark purple-brown. Gill extend- 

 ing along nearly the entire hind half of the right side. Length of 

 living animal 18 mill.; of alcoholic specimen 10; breadth 7J mill., 

 the foot 6 long, 3* wide ; gill 2 long. 



Shell comparatively very large, elongated, oval, flat, thin and 

 pale reddish, with the apex curved toward the right, and growth- 

 striae strong. Length of shell 6, breadth 2? mill. (Mart.). 



Fouquets, Mauritius (Mobius). 



Pleurobranchus scutatus MTS., in Mobius' Meeresfauna Mauritius, 

 p. 309, pi. 21, f. 8 (1880). Not P. scutatus Forbes, 1844. 



This apparently new species resembles Berthella porosa Blainv. 

 (see Gray, Figs. Moll. Auim., pi. 43, f. 1) in aspect, but is distin- 

 guished by the deep anterior cleft in the mantle. It is remarkable 

 that the smaller species of Pleurobranchus have, as a rule, relatively 



