132 M. K. A. Zittel on Fossil Calcispongice. 



Geol. Soc. 1877, p. 242) the microstmcture and characters of 

 the organization of Pharetrospongia Strahani, I extend this 

 name to a number of calcareous sponges of similar structure 

 and form which have hitherto generally been referred to 

 Cupulospongia, D'Orb., or Cupulochonia, From. Under these 

 names, however, the most different Hexactinellidge, Lithistidai, 

 and Calcispongiae have been thrown together ; so that it does 

 not seem advisable to maintain either of them. 



I have somewhat altered Sollas's diagnosis, and associated 

 with the typical species (P. Strahani), which consists of a 

 folded leaf, a series of cup-shaped sponges which agree in 

 their other essential characters. The genus has thus certainly 

 attained a wide extent and a somewhat vague limitation ; but 

 some unsuccessful attempts to break it up into several 

 genera have led me constantly back to the union of all the 

 forms cited below. Very frequently the state of preservation 

 causes notable differences which did not originally exist. 

 Thus, probably, all the species in which both surfaces are of a 

 rough and porous texture must have lost the smooth thin 

 epidermis, which is so beautifully preserved in certain speci- 

 mens from Farringdon, Essen, and Maestricht. 



The development or the absence of canals depends, on the 

 one hand, upon the size of the oscula and ostia, and, on the 

 other, upon the coarser or finer meshes of the skeletal network. 

 In Cupulospongia farringdonensis, for example, there is a 

 double system of efferent and incurrent canals, whilst other 

 species are entirely destitute of canals. 



If we give the genus Pharetrospongia. the increased exten- 

 sion proposed by me, it contains species from the Trias up to 

 the uppermost Cretaceous. 



a. From the Trias, 



1. Achilleum patellar -e, Munst. Beitr. iv. Taf. i. fig. 6. 



b. From the Jura. 



1. Spongia helvelloides, Lamx. Exp. Meth. pi. lxxxiv. 

 figs. 1-3. 



c. From the Cretaceous. 



1. Cupulochonia cupuliformis , From. Introd. pi. iii. fig. 5. 



2. Cupidospongia tenuipora, Rom. Spongit. Taf. ii. fig. 7. 



3. Chenendopora multiformis, Rom. ib. Taf. i. fig. 13, and 

 ii. fig. 2. 



4. Cupulochonia sequana, From. Cat. Rais. pi. iv. fig. 1. 



5. Cupidochonia tenuicula, From. ib. pi. iv. fig. 3. 



6. Cupulochonia profunda, From. ib. pi. iv. fig. 4. 



