6 J Canadian Arctic Expedition, 1913-18 



grey in colour, growing on a small bivalve mollusc-shell; R.N. II, from the 

 stomach of an Erignathus barbatus 73 inches long, consists of eight small speci- 

 mens, yellow in colour (orange when first obtained), irregularly rounded and 

 flattened in shape, the largest measuring 33 by 20 by 6 mm.; R.N. VIII consists 

 of a number of greyish, semi-digested fragments from the stomach of an Erignathus 

 barbatus; these were of a dark-green or orange-brown colour when first obtained. 



The surface of all the specimens is smooth and even; neither inhalant pores 

 nor oscula are visible. Texture firm, elastic and compact.. 



The skeleton consists of tylostyles, densely packed and arranged in great 

 confusion; there is a very opaque outer layer in which the cfentrotylote microxea 

 form an almost solid mass. 



Spicules. — (1) Tylostyles. Usually slightly curved, varying little in size, 

 and measuring up to 0-57 by 0-009 mm. In most cases the head is not very 

 marked, and some of them tend to become stylote. 



(2) Centrotylote microxea. Sometimes minutely spined or roughened; 

 the typical ones measure up to 0- 07 by 0-003 mm., but there are many smaller 

 and more irregular forms. 



Register Numbers, Localities, etc. — II: Station 37o, Dolphin and Union 

 strait at Bernard harbour. North West Territories, October 3,1 914. — ^IV: Station 

 41, Bernard harbour (outer harbour), 3-5 fathoms, sandy mud, July 20, 1915.— 

 VIII: Station 37a, Bernard harbour, August 24, 1914.— XII: Station 43&, 

 off Stapylton bay. Dolphin and Union strait. Northwest Territories, 25-30 

 fathoms, mud with pebbles, September 14, 1915. (All Canadian Arctic Expedi- 

 tion, F. Johansen coll.). — X: Whaler point, North Somerset island. Northwest 

 Territories, August 17, 1904, (Neptune expedition, A. Halkett coll.). 



Polymastia mammillaris (0. F. Mueller) Bwbk. 



(For discussion and synonymy vide Topsent (1900)). 



There are two much flattened, disc-shaped specimens in the collection; 

 Trichostemma-like, with marginal fringe of long spicules. The larger, (R.N.I, a), 

 which has a small pebble attached to the middle of the under surface, and 

 numerous teat-like projections on the upper surface, measures 63 mm. in dia- 

 meter and 5 mm. in thickness. The smaller (R.N.I, b) is attached to a shell 

 and measures only 25 mm. in diameter and 3 mm. in thickness. 



The colour in spirit is dark yellowish grey; in life it was "grey-yellow, with 

 the spine-brushes more strongly yellow-brown" (Johansen). The skeleton ar- 

 rangement and spiculation agree closely with those of specimens described 

 by Vosmaer and Topsent. 



Register Numbers, Locality, etc. — I, a, b: Station 43a, off Cockburn point, 

 Dolphin and Union strait. Northwest Territories, about 100 metres, mud with 

 pebbles, September 13, 1915. (Canadian Arctic Expedition, F. Johansen coll.). 



