1918] 



The Ottawa Naturalist 



27 



ON THE REMAINS OF A SELACHIAN FROM THE EDMONTON 



CRETACEOUS OF ALBERTA* 



By Lawrence M. Lambe, F.R.S.C, Vertebrate PALytoNTOLOcisT, 

 Geological Survey of Canada. 



The subject of the following remarks con- 

 sists of the caudal and hinder abdominal regions 

 of a selachian tentatively referred to the genus 

 Palaeospinax of the family Cestracioniidac. 



The specimen (field No. 5) is included in the 

 Geological Survey collection of 1915 from the 

 Edmonton formation on Red Deer river, Alberta, 

 and was obtained on the east side of the river, three 

 miles north of Tolman, at about 350 feet above the 

 river level. Its discovery was made by Mr. George 

 F. Sternberg in charge of the Vertebrate Palaeonto- 

 logical field party working in the beds of the above 

 formation during the season of 1915. 



These remains of a small shark occur on the 



It continues forward to near the anterior end of the 

 specimen where it is lost. Above it is clearly in- 

 dicated at intervals in the caudal region and for 

 some distance in advance of it, but is not seen farther 

 forward. 



The tail occupied about one-half the length of 

 the specimen and was preceded closely by the anal 

 fin of which the outline is clearly shown. At the 

 extreme anterior end of the specimen inferiorly 

 there are obscure indications of the pelvic fins and 

 certain fragments that may be the remains of 

 claspers, but they are too indefinite to allow of a 

 satisfactory conclusion being reached as to their 

 nature. 



INTERIOR 



EXTERIOR 



X 5 



X 5 



r'*^--.i 





INTERIOR 



EATER )OR 



X lO 



X \o 



\{^ 



^^ 



\m^^ 



If i| 1 / ,7\f ,7; 



^^ 



Central figure. Outline of type of Palaeospinax ejuncidu.s from tin- l<^ilmonton formation of Alberta. 



One-half natural size. 

 Upper figures. Sliagreen granules; interior and exterior surfaces. Five and ten times natural size. 

 Lower figure. Restoration of three vertebrae from front half of specimen to shew general proportions 



only. Twice natural size. 



weathered surface of a thick layer of hard grey 

 sandstone. About half the length of a slender fish 

 is represented, from the neighbourhood of the pelvic 

 fins to near the end of the tail, the tip not being 

 preserved. About 80 vertebrae had been present, 

 following each other in natural sequence in a length- 

 ened sigmoid curve, 245 mm. long, but onlv 30 of 

 them now parfiallv remain; manv of ^h" r'^-^i^inder 

 are represented merely by their impressions, and of 

 some no trace is left. The vertebrae extended 

 throughout the length of the specimen. See text 

 figures. 



The outline is well preserved below, especially 

 along the lobe of the tail where it is clear and sharp. 



Published with the permission of the Deputy 

 Minister of Mines. 



The body and fins were enveloped in shagreen 

 of which the granules were minute. The shagreen 

 is preserved throughout the tail except in its upper 

 front portion. In advance of the tail its continuity 

 is broken, but it is principally seen along the line of 

 the vertebral column, and dorsally and ventrally de- 

 fining the outline. 



The specimen lies with its left side in the rock 

 and it is the inner surface of the shagreen for the 

 most part which is exposed to view, and on which 

 the remains of vertebrae or vertebral impressions are 

 left. 



The vertebrae were apparently cyclospondylic in 

 character. They were higher than long, cupped at 

 either end, and constricted at the middle. The parts 

 that have resisted erosion consist principally of the 



