HIPPOTHOA EXPANSA. 291 



HippoTHOA EXPANSA, Dawson. 



Plate I. fig. 1. 



HippoTHOA EXPANSA, Dawson, " Cat. Anim. and Plants obseryed on the South- 

 east side of the St. Lawrence, from Quebec to Gaspe," &c. 

 By Robert Bell. PoIy::oa by Dr. Dawson. Geol. Survey 

 of Canada, Report of Progress for 1858 (published 1859), 

 255: Ncrman, Quart. Jom-n. Micr. Sc. 1868 (n. s.), viii. 

 216, pi. vi. figs. 1, 2. 



Zooecia large, ovate, elongate, ribbed transversely, and 

 traversed by delicate longitudinal striae, tapering below 

 into a tnbular stem ; aperture arched above, with a sinus 

 on the lower margin ; peristome slightly raised ; the 

 cells and fibre bordered by a calcareous expansion of 

 greater or less extent. Ocecia large, broader than high, 

 umbonate, borne on an imperfectly developed cell. 



Habitat. On small pebbles and stones, from moderate 

 depths to deep water (30-100 fathoms) . 



Locality. Off Unst, Shetland, on Pecten Islandicus, 

 100 fathoms (Jeffreys and Peach) . 



Geographical Distribution. Gulf of St. Lawrence, 

 common; Marsouin, north coast of Gaspe, in about 30 

 fathoms (Dawson) : Labrador ; Maine (Packard) : lat. 66° 

 59' N., long. 55° 27' W., in 57 fathoms (^Valorous' Ex- 

 pedition) . 



Range in Time. Postpliocene deposits, Beauport 

 and Riviere-du-Loup*, Canada (Dawson). 



From H. divaricata this species is distinguished by its 

 larger size (the cells are about half as large again as those 



* " The assemblage of shells at Riviere-du-Loup is in almost every parti- 

 cular that of the modern Gulf of St. Lawrence, more especially on its north- 

 ern coast." — Dr. Dawson, Notes on the Posfplioce?ie Geology of Canada, 

 p. 52. 



u2 



