442 Dr. J. E. Gray on the Classification of Sponges. 



excellently described and figured by Professor Lilljeborg, of 

 Upsala*, there is no difficulty in making a satisfactory com- 

 parison. Tins specimen was first named by Lilljeborg Balce- 

 noptera rohusta ; but it constitutes the type of the genus 

 EschricJitius of Gray — a designation which has been adopted 

 by its discoverer in his subsequent and more detailed descrip- 

 tion above referred to. It was found in a field, imbedded 

 partly in sand and partly in clay, at a depth of from 2 to 

 4 feet from the surface, 10 or 15 feet above the present sea-level, 

 and 840 feet from the shore, in conjunction with shells oi Mytilus 

 edulis and Tellina halthica of precisely the same appearance as 

 those now met with in the Baltic — indicating a period when the 

 general physical features of the sea were as at present, though 

 anterior to the elevation of the island to its present level. 



In size the Cornish specimen was slightly inferior to the 

 Swedish, the length of the mandible of the one being 7 feet 

 6 inches, of the other 7 feet 11^ inches (English) ; the remaining 

 bones bear a corresponding proportion. The entire length of 

 the Swedish skeleton was estimated at between 45 and 50 feet. 



A single cervical vertebra, in a mutilated condition, cast 

 ashore in Babbicombe Bay, Devonshire, in 1861, has been 

 referred by Dr. Grayf to the same species; and Mr. Cope 

 considers that a jaw-bone preserved at Rutger's College, New- 

 Brunswick, N.J., may belong to itf. 



These are the only known instances of the occurrence of 

 this whale, which, if extinct, must have become so at a com- 

 paratively recent period. Its systematic position is of much 

 interest, as it certainly cannot be placed in either of the three 

 principal genera into which the existing whalebone-whales 

 arrange themselves, viz. Balcena^ Megaptera^ and Balwnoptera^ 

 but is in some respects an annectent form, though with certain 

 peculiarities of its own. 



XLYIIL— iNToff^ on the Classification of the Sponges. 

 By Dr. J. E. Geay, F.R.S. &c. 



In the ' Proceedings of the Zoological Society' for May 9, 1867, 

 I published some notes on the arrangement of sponges, and 

 descriptions of some new genera — in which I divided the genera 

 into sections, orders, and families. 



In the present paper I propose to make an alteration in the 



* " On two Siibfossil Whales discovered in Sweden," Nova Acta of 

 tlie Pioyal Society of Sciences at Upsala, ser. 8. vol. vi. 1867; also Eecent 

 Memoirs on Cetacea (IJaj Society), 18C6, p. 278. 



t Catalogue of Seals aiid Whales in the British Museum, 18C6, p. 133. 



X Proc. Acad. Nat. Sc. Philadelphia, 1808, p. 194. 



