210 C. F. LASEKON. 



prominent, and the anterior very faint. Pallial line simple. 

 Hinge line very short and edentulous, the umbos sharp and 

 pointed. Ornamentation simple, concentric, but almost 

 smooth. 



Obs. The specimens on which this genus is founded are 

 two in number, one a testiferous left valve, and the other 

 a nearly perfect cast of a right valve. Both these specimens 

 are on the one slab, and were previously exhibited at a 

 meeting of the Linnean Society. 1 The remarkable truncate 

 anterior margin of this shell seems to separate it entirely 

 from nearly all the known pelecypods, and its characters 

 generally all seem to place it in a group by itself. The 

 family Lunulicardiidse of Fischer seems to be the only one 

 with which it possesses any affinities. 



Dall's 2 description of this family is as follows :— "Usually 

 equivalve, triangular shells with terminal beaks, from which 

 a sharp ridge runs toward the lower margin, bounding a 

 flattened area. Hinge margin straight, long. Internal 

 diant'-iers unknown." He mentions the following genera 

 as belonging to the family:— Lunulicardiiim, Munst; Patro- 

 cardium, Fischer; Mila, Tenka, Babinka (Matercula), 

 Amita (Spanila, Tetinka) of Barrande. 



Lately John M. Clarke' has described from the Devonian 

 of North America, a number of remarkable examples of 

 LuiiuUotu-dium, and some of these 4 show sharply 

 margins similar to Burrieva, but the < 

 other characters are essentially different. However, tlie 

 greatest interest is attached to Barrande's genera." These, 

 from the Silurian of Bohemia are all characterised by a 

 marked keeling of the lateral region. In every case, liow- 



' Pro.:. Linn. So.:, of X. S. Walt's. I 'Mi'.), vol. xxxiv, p. 118. 



• Zittel, Text-book of Palaeontology, vol. i, p. 367. 

 3 Naples Fauna in Western New York. 



* Notably L. clymeniae, plate 2, %. 5. 



5 Systeme Silurien de la Boheme fAcephales, 1882). 



