546 PEOE. W. J. SOLLAS ON SOME FOSSIL SPONGES 



thick, internal cayity J inch diameter. Incurrent ostia circular, 

 dispersed at about equal distances over the exterior, -fa—£s i ncn i R 

 diameter ; the excurrent ostia lie in longitudinal grooves, separated 

 by intervening ridges, on the internal surface of the sponge-tube. 



Plectospyeis majoe. (Plate XX. figs. 15 & 16.) 



Tubes larger than in the preceding species, | inch wide, wall 

 J inch thick, central cavity from J J to inch in diameter. 



Loc. Burton Bradstock. 



Hot. Upper part of the A. Parlcinsoni-zouQ. 



The preceding five sponges (Emploca ovata, Mastoclictyum Whid- 

 borni, Leptophragma fragile, Plectospyris elegans and P. major) do not 

 differ in any noticeable respect so far as the character of the skeletal 

 network is concerned, and the distinctions between them depend 

 wholly on the various habits of growth and differences in the canal- 

 system. It would be a quite natural arrangement to place them all 

 together among the Euretidae ; but, on the whole, it seems to me 

 better at present to refer them to different groups, according to the 

 classification of Zittel. 



Yenteiculitid^}. 



Calathiscus, gen. nov. 



A hollow horn-shaped sponge, with a somewhat wide central 

 cavity extending nearly the whole length. Incurrent ostia on the 

 outer surface more or less circular, thickly but irregularly dispersed ; 

 excurrent ostia on the inner surface irregular in shape and distri- 

 bution, markedly larger than the incurrent ostia. Incurrent and 

 excurrent canals forming tortuous branching cavities, interdigitating 

 with each other in the thickness of the walls, reminding one of the 

 canal-system in Dactylocalycc. Skeleton a very irregular network, 

 some of the nodes perforate, others imperforate, seldom if ever 

 regularly octahedral. 



Calathisctjs vaeiolattjs, sp. nov. (Plate XXI. figs. 17-20.) 



The most complete specimen is an irregular vasiform sponge, bent 

 from side to side alternately, and irregularly constricted and swollen 

 at intervals, the swellings or transverse ridgings apparently marking 

 stages of arrested longitudinal growth. It measures 7 inches in 

 length, and 1*5 inch in breadth at the distal end. The walls are 

 -J inch thick, the incurrent ostia from A% to -^ inch in diameter, 

 and the excurrent ostia from -^ to -J- inch in diameter. The prox- 

 imal end is not quite complete, and there is no evidence to show 

 whether the sponge was rooted or otherwise attached. 



Loc. Burton Bradstock. 



Hot. Upper part of the A. Parkinsoni-zone. 



Obs. The skeletal nodes are not regularly octahedral, as in the 

 Ventriculitidae generally ; but the general characters of the sponge 

 ally it more closely with that family than with any other. 



