1916] The Ottawa Naturalist. 93 



arrangement of the pinnules is incorrect. In 

 figure 4a, the series of small plates surrounding 

 the transverse food-groove is imaginary; the 

 figure evidently is based on figure 2b of the 

 Decade. 

 Jaeckel, Zeits, d.d. geol. Gesell. 52, 1900, p. 676. 



EXPLANATION of PLATE III. 

 Comarocystites punctatus Billings. Upper part of type figured by Billings 

 in his monograph on the Cystideae of the Lower Silurian rocks of Canada, in 

 Decade III, of Canadian Ovganic Remains, in 1858, where it forms figure 1 on 

 plate V. The specimen has. been crushed in a direction perpendicular to the 

 anal pyramid. Only the upper part of the right side of the theca is shown in 

 the figure here presented, magnified 3 d.amters. A considerable part of the 

 right posterior arm is exrosed. The brachials are numbered. The exposed 

 surfaces are interpreted as the dorsal side, most of the brachials showing the 

 facets for the attachmert of the pinnules on the right. The pinnules are 

 twisted so as to show both the narrow edges and the flat faces of the pinnulars 

 at different points along the pinnules. The first brachial and several closely 

 appressed pinnules belonging to the right anterior arm occupy the position 

 indicated by B. but can not be distinguished in the figure here presented. 

 Cover-plates may be seen along the right margin of the pinnulars marked D, 

 and along the corresponding margin of several pinnulars marked C in the 

 figure. The position of the anal pyramid and the smooth border of the sur- 

 rounding thecal plates is indicated at A. The surface of the thecal plates is 

 strongly weathered, except at the center, and indicates clearly the parallel 

 arrangement of all folds and pores of the mesostereom: these are perpen- 

 dicular to the same edge of the plates; consequently those groups which are 

 perpendicular to different edges form angles with each other along the 

 imaginary lines drawn from the center of the plates to the angles of the latter. 

 The passages of the folds and pores perpendicularly across the sutures from 

 plate to plate, in an apparently continuous manner, also is indicated. For the 

 remainder of the specimen, see the figure presented by Billings. Figure based 

 on photograph supplied by courtesy of the chief photographer of the Geological 

 Survey of Canada. The original specimen is numbered 1391 in the collection 

 of the Survey deposited in the Victoria Memorial Museum, at Ottawa. 



NEW SPILERIID^E. 



Dr. Victor Sterki has recently published in the Annals of the 

 Carnegie Museum (Vol. X, Nos. 3 and 4, pp. 429-474), a preliminary 

 catalogue of the Sphaeriidae of North America. The small bivalves of 

 this family are remarkably abundant in the vicinity of Ottawa, and 

 constitute no small part of the food of many fishes and birds. The 

 whole of the material submitted to Dr. Sterki has not yet been 

 thoroughly studied, and what was collected in 1915 and 1916 has not 

 yet been submitted to him. Most of the shells are minute in size, and 

 alike in colour, and for these and other reasons their determination is 

 attended with great difficulty, and, not infrequently, with doubt. The 

 trained eye of Dr. Sterki, and his keen mental apprehension of slight 

 differences, have in my opinion, rendered him capable of accomplish- 

 ing a task before which other have "backward shrank appalled." 

 While the result of his labors, as published, are modestly stated to be 

 tentative and preliminary, they undoubtedly constitute one of the most 

 valuable contributions made in recent vears to the studv of our inland 



