166 CALCAEEOUS SPONGES. 



Peronella clavakioides, Lamx. sp. (Plate XXXIII. figs. 6, 6 a.) 



1821. Spongia clavarioides, Lamx. Exp. method, p. 88, t. 84. f. 8-10. 

 1878. Peronella clavarioides, Zitt. Studien, III Ab. p. 32. 



In a transverse microscopic section of an example of this species from Ranville, the 

 fibres are clear, well defined, and equally disposed throughovit the wall ; they vary 

 from '07 to "2 mm. in thickness. They are composed of irregular three- and possibly 

 four-rayed spicules, heterogeneously mingled together. It is somewhat difficult, on 

 account of the close arrangement of the spicules in the fibre, to ascertain their dimen- 

 sions ; they appear, however, to be relatively large ; a single ray, partially visible, 

 measured "22 mm. in length and "036 mm. in thickness. 



Distribution. Middle Jura : Couche a Polypiers — Ranville, near Caen. 



Peronella mamillifera, Lamx. sp. (Plate XXXIII. fig. 3.) 



1821. Spongia mamillifera, Lamx. Exp. method, p. 88, t. 84. f. 11. 

 1840-47. Spongia mamillifera, Mich. Icon. Zooph. p. 113, t. 26. £. 5. 

 1854. Spongia mammillifera, Morris, Cat. Brit. Foss. p. 30. 

 1878. Spongites mamillatus, Queust. Petref. Bd. 5, p. 340, t. 131. f. 37, 38. 

 1878. Peronella mamillifera, Zitt. Studien, III Ab. p. 32. 



Sponges growing in depressed bushy masses, from 26 mm. to 60 mm. in width, and 

 about 32 mm. in height. The individual stems are subcylindrical or mammilliform, 

 from 6 to 8 mm. in diameter; the cloacal aperture at their summits is from 1"5 to 

 2 mm. in width, and in some instances three or four open furrows radiate from it. 

 The individual stems in some examples are nearly free from each other, whilst in 

 others only the coniform summits are free ; in a few instances a corrugated dermal 

 layer is present on the under surface of the sponge. 



The interior structure, as seen in a longitudinal section, is composed of narrow, 

 ill-defined fibres, about '1 mm. in width, which are arranged much closer near the 

 exterior than in the central portion of the stem. The fibres are now very crystalline, 

 and only show traces of three- or four-rayed spicules, with the rays disposed in the 

 central axis of the fibre. The spicular rays are from "1 to "2 mm. in length, and 

 about "03 in width. 



Distribution. Middle Jura : Couche a Polypiers — Ranville, L'Amouroux, near 

 Caen {coll. Tesson); Mont Terrible. Great Oolite: Hampton Cliff, near Bath 

 {Morris). 



Peronella tenuis, Hinde, n. sp. (Plate XXXIII. figs. 2, 2 «, 2 b.) 

 Sponges forming small bushy masses, of slender, cylindrical, bifurcating stems, from 

 3"5 to 5-5 mm. in thickness, either free or united nearly their entire length. The 

 cloacal aperture is about I mm. in width. 



