G4 ' SILICEOUS SPONGES. 



then, by the rules of priority, tlie term Siphonia will have to give place to one or 

 the other of the genera of Lamouroux which were published anterior to Goldfuss's 

 Siphonia. 



The genus Ckoanites, Mantell, 'Fossils of the South Downs,' 1822, p. 178, is of a 

 later date than the Hallirhoa of Lamouroux, besides which the term is inapplicable 

 to sponges like Sij^honia, for the first two species placed under the genus by 

 Mantell, Choanites subrotundus and flexuosus, are not Lithistid sponges at all, and 

 the type of Choanites is in reality a Hexactinellid sponge. 



SiPHONIA PIRIFORMIS, GoMfuSS. 



1853. Siphonia piriformis, Goldfuss, Petref. Th. 1, p. 16, t. 6. f. 7 a. 

 1878. Siphonia piriformis, Zittel, Studien, II Ab. p. 79, t. 9. f. 7. 



Non Siphonia pyr if or mis, Sowerby, Geol. Trans. 2nd ser. vol. iv. t. 15 a. 

 Non Siphonia pyriformis, SoUas, Quart. Journ. Geol. Soc. vol. xxxiii. t. 25. f. 1, 

 3, 4, 6, 8. 



Distrihution. Craie : Vaches Noires, Eanville, St. Adresse. 



Siphonia tulipa, Zittel. (Plate XIII. figs. 2, 2 «, 2 i, 2 c.) 



1878. Siphonia tulipa, Zittel, Studien, II Ab. p. 79, t. 9. f. 5. 



1836. Siphonia pijriformis, Sowerby, Geol. Trans. 2nd ser. vol. iv. p. 340, t. 15 a. 



1854. Siphonia pyriformis, Mantell, Medals of Creation, p. 231, f. 1-3. 



1877. Siphonia pyriformis, SoUas, Quart. Journ. Geol. Soc. vol. xxxiii. t. 25. f. 1, 3, 4, 6, 8. 



1878. Siphonia Websteri, Quenst. Petref. Bd. 5, t. 135. f. 15-19. 



Sponges simple or occasionally bifid, with conical or subcylindrical bodies, either 

 sharply constricted beneath the body or gradually tapering to a cylindrical stem 

 which usually branches at its termination. There is great variation in the size of 

 different specimens : a small form in the collection has the body only 21 mm. in 

 length by 13 mm. in width; a large specimen measures 105 mm. in length by 

 46 mm. in width. 



The cloaca is a narrow elongated tapering tube ; the aperture is narrow, with a 

 sharp margin, and about 8 mm. in width. It extends to the central or even the 

 lower portion of the body of the specimen. The arched canals which open into the 

 cloaca are about 1"25 mm. in width, whilst those extending from the outer surface to 

 the interior are very numerous, closely set, and average '5 mm. in width. Branching 

 canals radiating from the cloacal margins over the upper surface can also be distin- 

 guished in some examples. 



The spicules forming the interior meshwork of the body are mostly smooth-armed, 

 though near the extremities the arms, together with the minute branches, are 

 frequently tuberculated. The spicular arms are 'IBS mm. in length, measuring from 

 the centre to the point where they commence to divide, and '052 mm. in thickness. 



