358 Notices of Memoirs — Dr. J. F. Whiteaves — On MatheHa. 



11. — Description of a new species of Matheria (M. brevis)^ 

 FKOM THE Tkenton Limestone AT Ottawa.^ By Dr. J. r. 

 Whiteaves, F.Gt.S. 



THE genus Matheria was described by E. Billings in 1858, in th© 

 third volume of the Canadian Naturalist and Geologist. It 

 was based upon a single species, the M. tener of Billings, a small 

 lamellibranchiate or pelecypodous bivalve, from the Trenton Lime- 

 stone at Lake St. John, P.Q. Matheria appears to be most nearly 

 related to Cyrtodonta and Vanuxemia, and is now included in the 

 family Cyrtodontidse, Ulrich, of the order Prionodesraacea, Dall. 

 The types of M. tener, which were collected by Mr. J. Eichardson 

 and Dr. E. Bell in 1857 at Blue Point, on Lake St. John, are still 

 in the Museum of the Geological Survey. 



A second species of this genus, from the Trenton shales of 

 Minnesota, was described by Mr. Ulrich in 1892, under the name 

 M. rugosa, in the Nineteenth Annual Eeport of the Geological and 

 Natural History Survey of Minnesota. And, in his Eeport on the 

 Lower Silurian Lamellibranchiata of Minnesota, published in 1897, 

 in vol. iii, pt. 2, of the Final Eeport on the Geology of Minnesota, 

 Mr. Ulrich expresses the opinion that the Modiolopsis recta of Hall, 

 from the Niagara Limestone of Wisconsin and Illinois, is also 

 a Matheria. 



In the Museum of the Geological Survey there are a few specimens 

 of a fourth and previously undescribed as well as unfigured species 

 of this genus, from the Trenton Limestone of Ottawa, collected 

 many years ago by E. Billings, and labelled by him with the 

 manuscript name Matheria brevis. This species may now be defined 

 and characterized as follows. 



Fig. 1. — Matheria brevis. Side view of the moist perfect specimen collected, in 

 outline, and showing the marginal contour of the right valve. 



Fig. la. — The same specimen, as seen from above, to show the amount of convexity 

 of the closed valves. 



Both of these figures are of the natural size. 



Shell small, inflated, and regularly convex, but not quite as wide 

 as high, suboval or oblong subquadrate, about one-third longer than 

 high, and very inequilateral. Anterior side very short, narrow, and 

 consisting of a small rounded lobe below the beaks on each side ; 

 posterior side longer, and a little wider in the direction of its height ; 



^ Eeprinted from the "Ottawa Natui-alist," Journal of the Ottawa Naturalists'" 

 Club, vol. xvii (1903), pp. 33-34, May Number, Ottawa, Canada. 



