184 CALCAREOUS SPONGES. 



1878. Spongites rotula, Quenst. Petref. Bd. 5, p. 23i, t. 126. f. 1-41. 

 1876. Myrmecium hemisphericum, Zitt. Studien, III Ab. p. 38. 



In a vertical microscopic section of a specimen from Randen the fibres appear as 

 narrow anastomosing bands from -07 to -1 mm. in width ; the rays of irregnlar three- 

 or four-rayed spicules can be distinctly seen in the fibres. An average ray measures 

 •2 mm. in length by 'O-i mm. in vi'idth. 



Distribution. Upper Jura : Heuberg, Nattheim, Thurnau ; Heiligenstadt ; Basle ; 

 Randen. 



Myrmecium indutum, Quenst. sp. 



1858. Spongites indutus, Quenst. Der Jura, p. 098, t. 8-1. f. 21, 22. 

 1878. Spongites indutus, Quenst. Petref. Bd. 5, p. 245, t. 12G. f. 42-46. 

 1878. Myrmecium indutum, Zitt. Studien, III Ab. p. 38. 



Distribution. Upper Jura : Nattheim, Wiirtemberg. 



Genus LYMNOEEA, Lamx. 1821. 



Ltmnorea mamillosa, Lamx. (Plate XXXV. figs. 1, la, 1^.) 



1821. Lymnorea mamillosa, Lamx. Exp. method, p. 77, t. 79. £. 2-4. 

 1878. Lymnorea mamillosa, Zitt. Studien, III Ab. p. 39. 



Sponges growing in hemispherical or subspherical masses, from 15 to 25 mm. in 

 height and from 20 to 38 mm. in width. The basal portion is enveloped in a 

 concentric, wrinkled, compact dermal layer ; in some instances the base is concave. 

 The rounded upper surface is furnished with small conical, more or less projecting, 

 eminences, with a circular aperture, about 1 mm. wide, at the summit of each. In 

 a vertical section there are traces of concentric layers of growth. The canals, in 

 some instances at least, extend irregularly through the sponge. 



The fibres closely anastomose; they are about -12 mm. in width. In the transparent 

 sections which I have examined their structure is largely crystalline, but axial three- 

 or four-rayed spicules, with rays about -24 mm. in length, are clearly shown. In one 

 specimen the fibres on the summit of the sponge exhibit an open dermal layer of 

 spicules, probably four-rayed, similar to those of Tremacystia D'Orbignyi. 



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

 Caen. Inferior Oolite (Pea-grit) : near Cheltenham. 



Genus INOBOLIA, Ilinde, n. g. 



Sponges inverted conical, subspherical, or irregular in form, with convex summits. 

 The lateral surface in perfect specimens is inclosed in a compact wrinkled dermal 

 layer. No special canals appear to be present, and the summit only shows the 



