42 Dr. F. A. Bather on Protoechinus, Austin. 



type .... cannot be definitely located" (Jackson, 1912, 

 p. 454). 



Examination of the actual specimen would at any time 

 have enabled these distinguished authorities to come to a 

 more definite or more correct conclusion, and now that I 

 have succeeded in removing more of the matrix, it is possible 

 to give a fuller account than might have been anticipated. 



Description of Holotype. 



The fragment, which is of roughly triangular shape, 

 73*5 mm. X 41*5 mm., lies on a matrix of dark shaley lime- 

 stone, and is, or was, in part covered by the same. This 

 matrix contains numerous fragments of crinoids, a plate of 

 P alaeechinus , some brachiopod spines, and bits of Polyzoa. 



The portion of test preserved is viewed from the inner 

 surface. 



As represented in Austin's text-figure and in Plate II. 

 given herewith, the truncated apex of the triangle occupies 

 the peristomial region. Here there meet the adoral por- 

 tions of two ambulacral areas (B, D), enclosing part of an 

 iuterambulacrum (C). The accompanying text-figure (p. 18) 

 gives the outlines of the component plates, and the areas are 

 lettered in arbitrary fashion A to D. Of the interambu- 

 lacral area A, only two fragmentary plates are preserved. 



The Imbrication, as may be seen in the photograph, affects 

 both ambulacrals and interambulacrals, especially the 

 former. It follows the normal plan : an adoral overlap for 

 ambulacrals ; an aboral and adradial overlap for inter- 

 ambulacrals, which also cover the edges of the ambulacrals. 

 The imbrication of both is strong. 



Iuterambulacrum C begins with the primordial plate in 

 the basicoronal row, about 5*5 mm. long and wide. It is 

 succeeded in the second row by two plates. In the third 

 row appears a space for the initial plate of column 3, but 

 there is some disturbance at this point, and either the plate 

 has in whole or part been overturned so as to expose its 

 outer surface, or an interambulacral from the dorsal region 

 has been forced down upon it ; it will be seen in the photo- 

 graph that the outer margin of this plate on the left passes 

 over the edge of the adjacent plate in column 2 instead of 

 under it, as would be its normal position. That the initial 

 plate of column 3 did occupy this space is proved by the 

 existence of four plates in the fourth row. In the next row 

 appears the initial plate of column 5. Immediately below 

 this in the drawing are seen portions of what appear to be 



