Section IV., 1914. [n] Trans. R.S.C. 



On new species of A spider êtes from the Belly River formation of Alberta, 

 with further information regarding the structure of the carapace 

 of Boremys pulchra* 



By Lawrence M. Lambe, F.G.S., F.R.S.C, F.G.S.A., Vertebrate 

 Palaeontologist to the Geological Survey, Canada. 



(Read May 26, 1914.) 



A well preserved carapace of a turtle, belonging to the genus 

 Aspideretes, family Trionychidae, forms part of the Geological Survey 

 collection of vertebrates of 1913 from the Belly River formation on 

 Red Deer river, Alberta. All the bones which formed the shell 

 are intact and the sutures are very distinctly marked. The species 

 is apparently undescribed, and for it the name subquadratus is 

 proposed. 



The carapace is somewhat quadrangular, and broader than long. 

 In front and behind the outline is concave, laterally it is flattened, 

 and becomes broadly angular on each side of the anterior and posterior 

 emarginations. 



The matrix, a sandy clay, has not yet been removed from the 

 lower surface of the shell so that the present description will be con- 

 fined to the upper exposed part only. 



As the specimen now is, and it does not appear to be abnormally 

 flattened, or crushed, it is transversely convex with a sudden deflection 

 of the lateral border most pronounced at the middle of the sides. 

 In a longitudinal direction the shell is nearly flat with a slight inclina- 

 tion upward in advance of the first neural bone; the front and back 

 margins are acutely rounded. The maximum elevation of the shell 

 above the lowest part of the lateral downturned edge is about 29 mm. 

 The length of the carapace at the mid-line is 201 mm., and the greatest' 

 breadth 225 mm. 



In the mid-line are seven neural bones, preceded by a short 

 preneural. The costal bones number eight. 



The preneural is four-sided, broader than long, and broadest in 

 front. The first four neurals are six-sided, longer than broad, with 

 two postero-lateral short sides, at the front end of which the bone is 

 broadest. The preneural and the first and second neurals have 

 about the same breadth. The second neural is the longest. The 

 fifth and sixth are slightly irregular in shape, and longer than broad. 



*Communicated by permission of the Director of the Geological Survey. 



