194 Br. F. A. Batlter — Studies in Edrioasteroidea. 



In September, 1906, Dr. Whiteaves reprinted his original descrip- 

 tion, followed by a complete extract from the Treatise, in Paleozoic 

 Fossils, Tol. iii (pp. 316-21), published by the Geological Survey of 

 Canada. My drawings of Stega^ioblastus were also among the very 

 large number of text-figures which Messrs. Delage and Herouard 

 paid me the great compliment of reproducing in reduced facsimile in 

 their TraiU de Zoologie concrete, tome iii, " Les Echinodermes " 

 (pp. 415, 416, Paris, March 30, 1904). The Family Steganoblastidse 

 is accepted by Dr. F. Springer in the second edition of Eastman's 

 Zittel{\9U). 



The present paper gives the evidence on which my textbook 

 account was based. 



Material. 



The specimens are the three syntypes of Whiteaves, and may be 

 distinguished as A, B, and C. All were obtained from the Trenton 

 Limestone at Division Street, Ottawa. The precise horizon has 

 nowhere been stated. 



Specimens A and B were collected by Mr. John Stewart in 1886, 

 and are in the Victoria Memorial Museum, Ottawa. Specimen C 

 was collected by Mr. Walter R. Billings, in whose possession it 

 remains. 



A is an almost perfect theca with two columnals. It is the 

 original of Whiteaves' figs. 1 and 2, and of PI. XV, Eigs. 1, 3, 4, 6, 7, 

 in the present paper. It is hereby selected as the holotype. 



B is a theca crushed in the left anterior interradius and adjoining 

 radii, with portions of three columnals. It is the original of 

 Whiteaves' fig. 3, and of our PI. XV, Eigs. 2, 5. 



C is a much broken and crushed theca with no columnals. 



" All three of these specimens, when found, were," says Whiteaves, 

 " almost completely covered with a very tenacious shaly limestone." 

 This had been for the most part skilfully removed before the specimens 

 were sent to me, but the pores and the outlines of the plates were 

 still obscured. 



General Descrii'tion. 



The chief features can readily be gatliered from the slightly 

 restored figures 1 and 2, here reprinted, with slight modification, 

 from the Treatise (1900). 



The most obvious difference from Edrioasteroidea belonging to 

 the Family Edrioasteridae lies in the Stem of normal pelmatozoan 

 character. This supports a Theca of regular pear shape. 



The Theca consists, as in other Edrioasteroidea, of two systems of 

 plates : (1) an adoral system, (2) an adapical system. From the 

 tegminal region above the peristome, the Adoral System radiates in 

 the form of five subvective grooves, passing straight along the 

 perradial meridians, to a level almost exactly two-thirds of the way 

 down the long axis of the theca. From the stem, at the opposite 

 pole, the Adapical System spreads upwards, supporting and passing 

 in between the five grooves, to abut finally on the interradial 

 elements of the tegmen. In one of the interambulacral areas of this 

 system, lies the anus, marking the posterior interradius. 



