82 Mr. H. J. Carter on the Structure o/'Tethya dactyloidea. 



VII. — Additional Information on the Structure of Tethya 

 dactyloidea, Cart. By H. J. Caeter, F.R.S. &c. 

 [Plate X. figs. 1-5.] 

 This sponge (erroneously termed " sand-sponge," because it 

 grew in the sand, whereas the terra should rather be restricted 

 to sponges which build up their respective structures partly 

 with sand &c.) I described and figured in the ' Annals ' for 

 Jan. 1869, vol. iii. p. 15 ; and at p. 16 is the following line : — 

 " More detail I cannot offer, as I have given away the speci- 

 men." The fact is that I had left only the drawing and what 

 I remembered of the circumstances connected with the sponge 

 itself to assist me in retrieving for science all that I could glean 

 of this interesting form, which I found in the " land-wash " 

 on the south-east coast of Arabia, in the autumn of 1845, and 

 subsequently gave to one who could or will make no use of it. 



What the woodcut in the ' Annals ' shows of it, with the 

 exception of the spicule, is almost a facsimile of the sponge of 

 its natural size ; for I had taken care to secure this long before 

 I parted with the specimen ; and, with the exception of having 

 stated that this sponge was "hollow internally," the text is 

 equally correct. 



Searching, however, a few days since for an illustration of 

 the antheridium of Ghara in my journal, I came upon the 

 whole microscopic description, with illustrations and measure- 

 ments, of T. dactyloidea^ and thus am able to offer the addi- 

 tional information which will complete the description of this 

 interesting sponge. 



Omitting that which has already been published, the rest of 

 the matter in my journal runs as follows : — 



" July 1854. 



" The free extremity [of the sponge] is provided with a 

 large aperture, which may be seen to divide into several canals 

 a short way in. 



" When the shreddy twisted fibres of the base or root are 

 examined, they are found to be composed of bundles of long 

 spicules overlapping each other in spiral arrangement, respec- 

 tively surrounded by granular sarcode, and finally ending in 

 anchor-shaped extremities, which were originally imbedded in 

 the sandy bottom of the sea where the sponge grew (PI. X. 

 figs. 1 & 2). 



" When, again, the surface of the body is examined, the 

 projecting 'spicules there, which are in little tufts, are also 

 found to be long and flexible ; but their free extremities, in- 

 stead of being anchor-shaped, are all trifid extended, consist- 

 ing of one long and two short arms (fig. 3). 



