214 MESSRS. P. F. KENDALL AND R. G. BELL ON 



assuming the area affected to have extended 50 miles in a westerly 

 direction, we should have the whole of the " Lyonesse " ahove sea- 

 level, while if carried still further all the sea-bed between there 

 and Ireland would be laid dry. 



We trust that these views will not be looked upon as too specu- 

 lative. Probably the further investigation into the St. Erth deposit 

 which we desire to pursue may provide us with more direct evidence, 

 both physical and palseontological, regarding the peculiar deposit 

 which we have brought again under the notice of the Society. 



Appendix. 



On the Sjjonye-sjncules from the Deposits of St. Erth. 

 By Dr. G. J. Hinde, F.G.S. 

 The spicules occurring in the material are exclusively those of 

 Calcisponges, and they are completely detached from each other and 

 dispersed amongst the debris. They are all more or less imperfect, 

 having portions of one or more of the rays broken or worn away ; 

 and their surfaces in some cases show marks of erosion, but in other 

 instances they are as smooth as in recent spicules, and present an 

 equally glistening aspect under the microscope. Between crossed 

 nicols they exhibit the same chromatic effects as the spicules of 

 recent Calcisponges. In a few instances also axial canals of very 

 slender proportions can be detected. The spicules consist of slightly 

 curved acerates and three-rayed forms ; the rays of these latter are 

 straight or slightly curved, either subequal, or with two rays equal 

 and the third longer or shorter than the others (sagittate, Hackel). 

 There are also four-rayed spicules, the fourth, or apical ray as it is 

 termed, being apparently shorter than the others. On account of their 

 fragmentary condition, it is somewhat difficult to determine their 

 original dimensions with any exactness and, consequently, to refer 

 them to known species. * The acerate spicules are portions of large 

 forms; the longest fragment is 1*13 millim. in length by '066 

 millim. in thickness. In the smallest three-rayed spicules met with 

 the rays are -12 by '02 millim. ; but the rays of the majority of the 

 three- and four-rayed forms vary from "3 to '5 millim. in length 

 and from '016 to -083 millim. in thickness. In one or two excep- 

 tional forms the rays have a maximum length of -7 and a thickness 

 of •! millim. 



These spicules probably all belong to different species of the group 

 of Leucones, Hackel. Some correspond in form and size with those 

 of Leuconia Johnstonii, Carter, and others with Leucandra caminus, 

 Hackel, whilst one or two differ slightly from those of any recent 

 species with which I am at present acquainted. The former of 

 these two species now exists on the coasts of Ireland, Yorkshire, 

 Devonshire, Guernsey, and Sark, and the latter on the coasts of 

 Devon, Norway, Portugal, the West Indies, and Labrador. 



The occurrence of spicules of Calcisponges so abundantly in this 

 deposit tends to negative the opinion, expressed more especially by 

 Mr. Carter, that the spicules of these sponges are too unstable to be 

 preserved in the fossil state. 



