370 ESCHARIDJE. 



the base, and becoming mucb contracted towards the 

 mouth, which is placed at the summit. The primary aper- 

 ture is a simple opening, narrow between the upper and 

 lower margins, but elongated transversely. In an early 

 stage of growth the denticle is very apparent ; but by the 

 subsequent development of the lower lip, which rises into 

 a broad and prominent expansion, the mouth is partially 

 concealed, and it is then difficult to detect. The texture 

 of the cells is dense ; and so minute is the granulation of 

 the surface that they appear almost smooth. They have a 

 polished and glossy appearance. The full number of the 

 marginal spines appears to be three ; but there are often 

 only two. 



" The form of the ovicells and mouth in the fertile cells 

 reminds one forcibly of a helmet with the vizor raised " 

 {Norman) . 



In a fine specimen of the present species from the St. 

 Lawrence, which I owe to Dr. Dawson, the cells are much 

 more convex and distinct and deeply divided than in the 

 Shetland form, and more elevated towards the oral extre- 

 mity. The ovicell is also more decidedly thrown back oft" 

 the mouth. 



MucRONELLA MICROSTOMA, Normau. 



Plate XXXVIII. figs. 3, 4. 



Lepualia microstoma, Norman, Ann. N. H. ser. 3, xiii. 87, pi. xi. fig. 2 ; 

 Rep. Brit. Assoc, for 1868, 307. 



Zoivcia flask-shaped, very distinct, tumid, the oral extre- 

 mity elevated, free, contracted into a short neck ; sur- 

 face smooth or finely granular; orifice small, contracted, 

 much broader than long; peristome thickened, nar- 

 rowed, much raised and everted in front, and on the 

 upper margin rising to a central point. Ooecia globose, 

 tumid, set far back, minutely granular. 



