1869.] DR. J. 8. 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 Dactylocalyzx ; 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 laminee on the lower sur- 
face.’’ 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 cal- 
locyathes 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 Mu- 
seum which probably belong to the same species. The smaller one 
was collected by the Rev. L. Guilding at St. Vincent’sin 1840; and 
the other was received from the West Indies by Mr. Scrivener in 
1842.” On examining microscopically the structures of the speci- 
men 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 erro- 
neously attached it. 
The specimen from ‘‘ Mr. Scrivener in 1842 ” is identical in struce- 
ture with Dr. Gray’s type specimen of his genus Myliusia, both as 
regards generic and specific characters, and should therefore be ar- 
ranged with that sponge as [phiteon callocyathes. 
Myutvusta Grayit. 
Myliusia callocyathes, Gray, P. Z. 8. 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 mi- 
nutely spinous. Interstitial spicula numerous, acerate, large and 
long, variable in size; disposed in lines at right angles to the strati- 
