102 SILICEOUS SPONGES. 



This genus resembles Stauronema in the robust character of its spicular mesh, but 

 diflfers therefrom in the absence of a dermal layer and the perforate character of the 

 canals. The only specimen exhibits the spicular structure and the outer surface very 

 perfectly, but the interior is infilled, and quite concealed by the matrix. 



Sestrodictton convolutum, Hinde, n. sp. (Plate XXV. figs. 2, 2 a.) 



The funnel-shaped sponge, which is imperfect at the base, measures 68 mm. in 

 height and 84 mm. in width at the summit. The canals are ovate in form, about 

 ]-75 mm. in their greatest di;imeter; the distance between the rows is about 1"3 mm. 

 The spicules of the mesh have smooth arras ; the distance between the nodal 

 centres is "3 mm. Small pointed spines, apparently the free arms of the spicules 

 bordering the canals, pi'oject from the walls into the canals. 



The outer surface characters of the specimen are so perfectly preserved, that if any 

 dermal layer had existed, one can hardly doubt but that traces of it would have 

 remained. 



Distribution. Alpine Chalk ( = Upper Green Sand) : High Sentis, Canton Appenzell. 



Genus BRACHIOSPONGIA, Marsh, 1867. 



Brachiospongia bigitata, B. Owen, sp. 



1857. Scyphia digitata, D. Owea, Second Report on the Geol. of Kentucky, p. 111. 



1838. Description d'un fossile, Troost. Mem. de la Soc. Geol. de France, Tome 3, t. 11. 



£. 8, 9, 10. 

 1867. Brachiospongia Rcemerana et Lyonii, Marsh, Am. Jouru. Science and Arts, 2 ser. 



vol. 44, p. 88. 

 1878. Brachiospongia, Zitt. Handb. der Pal. Bd. 1, p. 173. 

 1880. Brachiospongia Rcemerana, P. Rcemer, Leth. geog. 1 Th. p. 319, fig. 61. 



Up to the present nothing definite is known of the spicular structure of this extra- 

 ordinary sponge, and its true characters and position are therefore uncertain. By 

 Prof. Zittel it has been provisionally placed in the family of the Euretidae. The 

 Museum only possesses a cast. 



Distribution. Cincinnati Group : Kentucky. 



Family C0SC1N0P0RID.E. 



Genus LEPTOPPIRAGMA, Zittel, 1877. 



Leptophragma Muechisoni, Gold/., sp, 



1826-1833. Scyphia Murchisoni, Goldf. Petrcf. 1 Tli. p. 219, t. 65. f. 8. 

 1877. Leptophragma Murchisoni, Zitt. Studieu, I Ab. p. 48; Neues Jahrbuch, p. 357, 

 t. 3. f. 1. 



