86 



an obsure mesial elevation in front, corresponding with the sinus of the ventral valve ; the 

 beak incurved, and buried beneath that of the ventral valve. Surface with numerous very 

 delicate concentric lines of growth, which become crowded together and conspicuous towards 

 the front margin. 



This species is somewhat variable in shape ; some specimens have their greatest width a 

 little in front of the middle of the shell ; but others (and these are perhaps the commonest) 

 have the greatest width at about two-thirds of the distance from the beak, or even nearer the 

 front than this, the shell thus assuming a sub-triangular form. Average specimens have a 

 length of six lines, a width of five lines, and a depth of about three lines. 



In the most perfect specimens I have seen, the foramen is large and conspicuous, and is 

 perforated in the summit of the beak of the ventral valve, so as to look upwards. 



Locality and Formation. Rare in the Corniferous Limestone of Port Colborne. Hamil- 

 ton formation of Widder. 



104. SPIRIGERA SCITULA (Hall). 



Atrypa scitula (Rail), Report on the Fourth Geol. Dist. New York, p. 171, Fig. 1. 



Athyris (?) scitula (Billings), Canadian Journal, New Series, Vol. V., p. 278, Figs. 35, 

 36 (f.cet. exclusis). 



1 Meristella scitula (Hall), Pal New York, Vol. IV.. Plate XLVIL, Figs. 34-36. 



Shell ovate, both valves convex, the ventral valve the most so, somewhat compressed to- 

 wards the front. Ventral valve with a prominent beak, which is incurved over that of the 

 dorsal, valve, and is perforated by a conspicuous foramen. Dorsal valve most convex above 

 the middle, depressed towards the front, with a small beak, which is buried beneath that of 

 the dorsal valve. Surface marked by fine concentric stria;. Length of an average example one 

 inch ; width, nine lines ; depth, six lines. 



I have only one well preserved example of this species, and am therefore, not prepared 

 to discuss its affinities. Hall's species certainly seems to me to be identical in part with that 

 figured by Mr. Billings. The Charionella circe of Mr. Billings appears to me to be quite dis- 

 tinct, though it is asserted by Hall to be identical with his Meristella scitula. 



Locality and Formation.- ~ Rare in the Corniferous Limestone of Port Colborne. 



Genus ATHYRIS (McCoy). 



Shell variable in shape, the valves unequally convex, with or without a mesial sinus end 

 fold, articulated by teeth and sockets. Beak of the ventral valve incurved, usually overly xg 

 and in contact with the beak of the dorsal valve, not perforated by a foramen, or with the 

 foramen concealed when fully grown. " In the interior of larger or ventral valve the dental 

 plates are fixed to and along the sides of a longitudinal prominence or convex arch-shaped 

 plate, which extends to less than a third of the length of the shell, with its narrow end fitting 

 into the extremity of the beak, and its lateral diverging edges to the bottom of the valve. 



" The interior of the smaller or dorsal valve is partly divided by a large, deep 



longitudinal septum, which extends from the extremity of the umbo to about two thirds of 

 the length of the shell, supporting at its origin the hinge-plate, which is divided into two por- 

 tions by a narrow gradually widening channel ; to the socket ridges are affixed the spiral cones, 

 the extremities of which are directed towards the lateral margin of the shell ; on either side 

 of the septum are seen two muscular scars formed by the adductor " (Davidson, British Fossil 

 Brachiopoda, General Introduction, p. 85.) 



Accepting the above definition of the genus Athyris, there are only two forms which have 

 come under my notice in the Devonian Rocks of Ontario, which appear to be referable to this 

 genus, and the position of one of these somewhat doubtful. The forms in question are Athyris 

 nasuta (Conrad sp. = A. clara, Billings), and A. Maia (Billings), of which the last is referred 

 by Hall to the genus Spirifera. 



105. ATHYRIS NASUTA (Conrad). 



Atrypa nasuta (Conrad), Ann. Report on the Palaeontology of New York, p. 18. 

 Meristella nasuta (Hall), Thirteenth Report on the State Cabinet, p. 93. 

 Meristella elissa (Hall), Fourteenth Report on the State Cabinet, p. 100. 



