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Show 1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 335 The stratified character of the reticulating skeleton of the type sponge of this genus, when viewed in a section at right angles to its natural surface, with a microscopical power of 100 linear, at once separates it from the unsymmetrical structure of Dactylocalyx ; and although participating with Iphiteon in the character of symmetrical arrangement of its skeleton, it is equally well distinguished from that genus by the total absence of the confluent areas that are so characteristic in those sponges. In a paper read before this Society, November 22, 1859, by Dr. J. E. Gray, entitled " Description of MacAndrewia and Myliusia, two new forms of Sponges," and published in the ' Proceedings' of the Society for that year, page 437, the author has described his genus Myliusia, page 439, and has figured in plate xvi. Radiata, of the same volume, his species Myliusia callocyathes as the type of his genus ; subsequently, in the ' Proceedings' of this Society for 1867, p. 506, in his " Notes on the Arrangement of Sponges," he has given the following characters as those of the genus;-" The sponge conical, cup-shaped, pierced with numerous short truncated tubes, forming raised folded anastomosing laminae on the lower surface." This description applies only to the external characters of the skeleton, entirely omitting all the other anatomical peculiarities of the sponge. On microscopically examining the structures of the type specimen I found them to be identical with those of the genus Iphiteon, and I have therefore arranged Dr. Gray's Myliusia callocyathes as Iphiteon callocyathes in the present paper. In Dr. Gray's "Notes on the Arrangement of Sponges," p. 506, he states that, " There are two small specimens in the British Museum which probably belong to the same species. The smaller one was collected by the Rev. L. Guilding at St. Vincent's in 1840 ; and the other was received from the West Indies by Mr. Scrivener in 1842." On examining microscopically the structures of the specimen collected by the Rev. L. Guilding at St. Vincent's, I found it to differ widely in the construction of its skeleton from either Iphiteon or Dactylocalyx, and I therefore propose to apply Dr. Gray's genus Myliusia to this species in place of the one to which he has erroneously attached it. The specimen from " Mr. Scrivener in 1842 " is identical in structure with Dr. Gray's type specimen of his genus Myliusia, both as regards generic and specific characters, and should therefore be arranged with that sponge as Iphiteon callocyathes. MYLIUSIA GRAYII. Myliusia callocyathes, Gray, P. Z. S. 1859, p. 439, et 1867, p. 506. . Sponge sessile, massive. Dermal surface unknown. Surface of rigid skeleton uneven and excavated. Oscula, pores, and expansile dermal system unknown. Skeleton stratified, forming a series of expanded crypt-like spaces. Fibre cylindrical, incipiently or minutely spinous. Interstitial spicula numerous, acerate, large and long, variable in size; disposed in lines at right angles to the strati- |
