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Knowledge of the Spongida. 365 



grammatized Tethya cranium here point to the embarrass- 

 ment caused by the introduction of " Tetilla " for Tethya ?), 

 it is represented as wrinkled by transverse elevations, " Quer- 

 hockern und Kunzeln " (Spong. Atlantisch. Geb. p. 66, 

 Taf. vi. fig. 9). Here I would observe that a sharp turn in 

 the direction of a spicule often presents itself under the illusory 

 form of a globular inflation ; hence one termination of the 

 bihamate has been represented in this way in Dr. Bowerbank's 

 illustration of Tethya cranium (Mon. B. S. vol. iii. pi. xiv. 



Besides the sessile species of Tethyina, ex. gr. the type 

 species Tethya cranium , there are pedicellate or rooted ones. 

 Tetilla euplocamus, Sdt., to which I have already alluded, is 

 one of these, in which the anchoring-spicules are twisted into a 

 cord for about half an inch, like those of Tethya dactyloidea, 



Crtr. ('Annals,' 1869, vol. iii. p. 17, fig. 1, b), before they 

 become separated into a lash for fixing-purposes in the sand 

 or mud of a soft sea-bottom, as with the cord of Ilyalonema. 

 In Tetilla poly lira, Sdt., which came from Iceland, they are 

 not twisted into a single cord, but proceed at once to their 

 destination in little tufts which issue from papillary eminences, 

 into which the lower part of the body is divided, recalling to 

 mind the radical cords of Thenea Wallichii &c. Long before 

 either of these were described I had found Tethya dactyloidea 

 on the south-east coast of Arabia (viz. in Dec. 1844), but did 

 not publish my description and illustration of it until 1869 ; 

 and then 1 had mislaid part of it, which was not found until 

 1872; hence the first part appears in the former year ('Annals,' 

 vol. iii. p. 15) and the other in the latter (' Annals/ vol. ix. 

 p. 82) . I afterwards found it in the Maham estuary at Bom- 

 bay, which is also sandy; and just now have received several 

 specimens from the sea about King's Island, off the coast of 

 Burmahj which has a mud-bottom. Thus the radiciferous 

 form of Tethya appears to be very general. Besides Tethya 

 dactyloidea and T. merguiensis there is a robust form of Tethya 

 cranium, which grows on the rocks about King's Island, and 

 in my MS. report of the sponges there, to which I have already 

 alluded, has been designated " var. robusta" in which the 

 excretory canal-system in its cavernous character resembles 

 that of Thenea Wallichii and. Ilyalonema Sieboldii, but, instead 

 of opening into a central cloaca, ends in a series of very large 

 vents situated round the lower third of the sessile globular 

 sponge. However, in the radiciferous form there is a short 

 cloaca with single wide osculum at the summit as in Thenea 



Wallichii. 



