from the South Coast of Devon. 5 



throughout the sponge, but chiefly brought together in the 

 spiculiferous layer ; the minute spinous one also, but chiefly 

 confined to the dermal layer, and the tricurvate spicule con- 

 fined to the body-substance. 



Size variable ; largest specimens found, about 4 inches in 

 diameter and a little under an inch in thickness. Black cells 

 variable, largest about l-170tli of an inch in diameter. Shaft 

 of largest spicules about l-80th inch long. Spinous spicule 

 about 1-1 200th inch long ; tricurvate about 1 -300th inch long. 



Log. Budleigh-Salterton, south coast of Devon, Straight 

 Point. 



Hah. Fine red-sandstone conglomerate rocks of the New Red 

 Sandstone series. About two-thirds below high-water mark 

 and downwards ; on inclined surfaces, deep in under the 

 bowers of the rocks, never pendent from their under surfaces. 



Obs. This sponge, if not the same, is closely allied to Hi/- 

 meniacidon Bucklandij Bowerbank (Brit. Spong. vol. ii. p. 226), 

 but wrongly classed, as conjectured by the author in the fol- 

 lowing passage at the end of his description, viz. : — 



" This sponge varies so widely from the ordinary structure 

 of Hymeniacidon that I doubt much whether it should not be 

 made the type of a new genus." 



Now there is no doubt in my mind about the matter, nor 

 could there have been in Dr. Gray's when he proposed a place 

 for this sponge among his Tethyadas (Notes, &c. I. c. p. 542, 

 1867) under the new name of " Dercitus.'''' Schmidt sub- 

 sequently (Spong. Algier, p. 15, 1868) proposed the name of 

 " Pachastrella " for this genus in his Compagineag, finally 

 placing it among his Corticatse, i. e. under Ancorinidje, in 1870 

 (Spong. Faun. Atlantisch. p. 64) ; but he errs in his note to 

 Dr. Bowerbank's synonymy (p. 76), where he considers the 

 presence of the tricurvate spicule " accidental," as may be 

 seen by my description and illusti'ations ; nor is Schmidt 

 right in stating that this kind of spicule belongs to the 

 character of his Desmacidinas, if this remark means exclu- 

 sively ; for he himself has figured a tricurvate spicule as partly 

 'characteristic of his Pachastrella connectens (Spong. Faun. 

 Atlantisch. Taf. vi. fig. 5). Dr. Gray's aiTangement therefore 

 claims priority; and hence the name of "DerctVi/s" for this 

 genus. 



The dried specimen, from Guernsey, which was sent to and 

 described by Dr. Bowerbank under the name oi Hymeniacidon 

 Bucklandi was of a " dark purple colour " externally, and 

 internally " light brown ;" and all that is stated of the speci- 

 men that was sent to him, preserved in salt and water, from 

 Torbay is that it was '' almost as solid as a piece of boiled 



