24 Mr. W. J. Sollas on Stauronema, a new 



2. Stauronema lohata {xn\\\\) . 



Form. Posterior mass not extending laterally as far as tlie 

 lateral edges of the attached oscular plate, seldom or never 

 ridged horizontally, usually lobed vertically into two or more 

 div^erging processes. 



Oscides smaller than in S. Carteri. 



Remark. This species is characterized by a more variable 

 and less regular form than >S'. Carteri. 



EXPLANATION OF THE PLATES. 



Plate I. 



[All the figures of this plate represent the objects of their natural size.] 



Figs. 1 to 4. Stauronema Carteri. 



Fiy. 1 . An average-sized specimen, anterior aspect : o, oscular plate ; 



p, posterior mass ; s, seam or line of division between the two. 

 Fig. 2. Same specimen as fig. 1, posterior view : b, base ; u, posterior face 



of projecting oscular plate ; e', excurrent canal crossing oscular 



plate, shown on a fractured surface ; s' s', Ime of termination of 



posterior mass against the oscular plate. 

 Fiy. 3. A smaller specimen, anterior view. 

 Fig. 4. Same specimen, posterior view : h, base. 



Figs. 5 to 8. Stauronema lobata. 



Fig. 5. Anterior view of a medium-sized specimen : ^y, a lobe projecting 

 from the posterior mass. 



Fig. 6. Posterior view of preceding specimen : h, a fi-agment of attached 

 " coprolite." 



Fig. 7. Posterior view of a specimen showing the diverging lobes of the 

 posterior mass, with the oscular plate visible between them. 



Fig. 8. A very gently curved, almost flat specimen, showing the free sur- 

 face of the oscular plate with its pore-areas. 



Fig. 9. Free sponge-plate : l-n, simple outline of its surface ; n n n, ori- 

 ginal margin (the remaining edge is a broken one) ; a, detailed 

 representation of the oscular markings which cover the whole 

 surface of the plate. 



Plate IL 



Fig. 1. Transverse section through StauronemaCurter% : o, oscular plate ; 

 p, posterior mass ; «, b, & c, directions along which other sections 

 were made through the same specimen — o, longitudinal, i&c, 

 parallel sections ; e &e', excurrent canals. Nat. size. 



Fig. 2. Longitudinal section through the centre of another specimen of 

 *S'. Carteri : o, p, e, & e',_ as in fig. 1 ; d, distal edge of oscular 

 plate ; r, outhne in section of ridges formed by an accumulation 

 of the superficial network. Nat. size. 



Fig. 3. Parallel section through the oscular plate along the line c in fig. 1. 

 Nat. size. 



Fig. 4. Skeletal network of oscular plate, magnified from fig. 2 : a, margin 

 of fibre, transparent as far as b, where it becomes granular ; 



