HOSS fs Om eH CAMB RIAN. 
PROSPECT MOUNTAIN GROUP. 
PORIFERA. 
Genus PROTOSPONGIA Salter. 
Protospongia fenestrata Salter. 
Plate ix, figs. 5, 5 a, b. 
Protospongia fenestrata Salter, 1864. Quart. Jour. Geol. Soc., vol. xx, p. 238, pl. 13, 
fig. 12 a, b. Ibid., Cat. Cambrian and Silurian Fossils, p. 
3, 1873. 
Hicks, 1874. Quart. Jour. Geol. Soe., vol. xxvii, p. 401, pl. 
16, fig. 20. 
Zittel, 1877. Abh. der K. bayer. Akademie der Wiss. 2 Cl., 
xili; Bd. “Studien ii, fossile Spongien” (p. 45, sep. copy). 
Carter, 1877. Ann. and Mag. Nat. Hist. ser. 4, vol. xxv, p. 177. 
Brégger, 1878. On paradoxidesskifrene ved Krekling. Sep- 
arataftryk af Nyt Magazin for Naturvidensk. vol. xxiv. ity oy 
20, t. 6, f. 14. 
Sollas, 1880. Quart. Jour. Geol. Soc.. vol. xxx vi, p. 362, figs. 
1: 2 
Roemer, 1880. Leth. Geogn., 1 Th. p. 316, f. 59. 
Hinde, 1883. Cat. Fossil Sponges, p. 129, pl. xxviii, fig. 2. 
Mr. Salter originally described this interesting sponge as having a 
loosely reticulate skeleton formed of very large cruciform spiculz, the 
branches of which cross each other at an angle of 80°, and only in one 
plane, no ascending or descending branches rising from the point of con- 
junction. The angles occasionally vary, but not much. 
More perfect specimens obtained by Dr. Hicks show the spiculze to be 
quadriradiate, slightly raised at the center and formed of four nearly cylin- 
drical rays. 
The skeleton, as described by Mr. Sollas, is composed of large primary 
spicule with the interspaces filled in by three series of spicule, each 
u 
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