82 



above the general surface ; area of moderate size, flat, extending to the 

 cardinal angles, forming with the plane of the lateral margin an obtuse 

 angle of about 135° ; foramen open to the beak, about as wide as high. 

 Dorsal valve gently convex-, with a wide shallow mesial depression extend- 

 ing to the beak ; area half the size of that of the ventral valve ; inter- 

 rupted in the middle by a double divaricator process similar to that of 

 Leptoe7ia sericea; forming with the ventral area an angle of about 90°. 



Surface of the specimen not well preserved, but it appears to have a 

 number of fine distinct ribs with smaller ones between as in S. aUernata, 

 the whole crossed by numerous rugose concentric squamae of growth. 



Length of the specimen 4| lines ; width 5| lines ; height of the ventral 

 area of the foramen f of a line. 



Of this singular species only a single specimen with the valves attached 

 has been collected. The ventral valve is remarkably like that of a Lep- 

 tcena or jStrophomena, but the dorsal valve is that of an Orthis externally, 

 while the place of the foramen is occupied by a divaricator process which 

 has so far as it can be seen the structure of the same organ in L. sericea. 

 It seems to belong to a group connecting Orthis with /Strojyhomena. 



Locality Siud Formation. — Point Levis. In the upper part of limestone 

 No. 2, Quebec group. 



Collectors. — Sii' W. E. Logan, J. Richardson, R. Bell. 



Orthis Mycale. (N. sp.) 



Fig. 75. 



Fig. 76. 



Fig. 75. — Orthis Mycale. — b, Dorsal valve ; a, muscular impression enlarged. 



76. — Eudocia. — a, Ventral view ; 6, side view ; c, interior of ventral 



valve. 



Description. — Shell transversely semi-oval, proportionally very wide ; 

 hinge-line equal to the greatest Avidth of the shell ; cardinal angles 

 somewhat acute, about 75°; sides straight, gently convex or gently concave 

 for about half the length, then gradually curved round to the front margin, 

 which is gently rounded or straight in the middle. Ventral valve mode- 

 rately convex, with the cardinal angles largely compressed ; beak depressed 

 below the greatest height of the shell ; area small, forinmg with the plane 



