REPORT ON THE MAESENIADJS. 21 



true Marsenice. The whole rostrum, the mouth-tube, was as usual (fig. 12, a). The whitish 

 bulbus pharyngeus (fig. 1 2) exhibited the ordinary characters ; it was about 3 mm. long by 

 2 "5 broad and 2 thick ; the cartilaginous or tendinous patches (fig. 12, b) lay as usual on the 

 hinder end, and the Musculi laterales, superior and inferior (fig. 12, b) had the normal 

 relations. The usual radula sheath (fig. 12, d) projected from the cleft posterior end ; when 

 unrolled and extended it measured approximately 5 mm. The sides of the downward- 

 directed, slit-like, internal mouth (fig. 13, a) each bore a firm, dull horny-yellow lip plate, 

 somewhat narrowed anteriorly and posteriorly, and attaining a length of about 0'6 mm. (fig. 

 13, b, b). The ends of the plates did not meet. The plates were composed of as many as 

 twenty, closely packed, indistinctly separated rows of rods, which attained a height of as 

 much as '06 8 mm., and were slightly bent above (fig. 14). The whole internal surface of the 

 external mouth opening was lined by a colourless, somewhat thick cuticle, shining through 

 which the ends of the epithelial cells were visible, producing a tabulated appearance (fig. 1 5). 

 The yellow radula (fig. 16) bore 20 rows of tooth plates, 9 of which were covered, while, 

 within the sheath, there were 30 developed and 5 immature rows, making a total of 55. 

 The tooth plates were of a bright yellow colour ; the median attained a length of 

 - 12 mm., the lateral had a maximum height of 0"18, and the first (innermost) and second 

 external plates measured respectively 0"17 and 0"16 mm. The sides of the median plates 

 were usually parallel, four or five denticles lay on each side of the strongly developed point 

 (figs. 16, a, 17, 18, 20, a). The form of the lateral plates (figs. 16, b, b, 19, a, 20, b) was 

 essentially the same as that in the Marseniadse generally. The basal portion was bevelled, 

 and had a compressed conical shape, the point was turned upwards and inwards, and bent 

 in a somewhat hook-like curve. The under surface of the basal portion (fig. 20, b) was 

 broad and almost square, and in front of this lay the cleft which received the hook of 

 the basal portion of the tooth in front (fig. 20). The basal portion passes into the 

 small hook (fig. 19, a), which is bent almost at right angles and exhibits a strong sharp 

 point; the hook has usually 6 to 12 or sometimes only 4 to 5 small denticles on the 

 posterior upper margin, and almost always 4 of a coarser character on the turned-down 

 anterior lower edge (figs. 16, b, b, 19, a). On the outside of the lateral plates, the first 

 external plate was hook-shaped, upright, and strongly developed, with a broad and some- 

 what peculiar basal surface (figs. 19, b, 21, a); the second external tooth, outside the 

 former and a little behind it, was less strongly developed, and had a smaller, simpler 

 base (fig. 21, b). Both these external tooth plates were entirely destitute of denticles. 



The esophagus (fig. 12, e, 22, a) was wide, and dilated into a sort of crop posteriorly 

 and inferiorly (fig. 22, b). The second crop which always occurs in the true Marsenice was 

 here entirely absent. The yellowish-white foliated stomach (fig. 22, c) was as usual hemi- 

 spherical, was somewhat markedly concave on the anterior side, measured about 2*5 in 

 length, 4*5 in maximum breadth, and as much as 2*25 mm. in height, and exhibited the 

 ordinary foliated structure. The folia themselves were as usual ; they seemed only 10 in 



