Prof. P. M. Duncan on the Genus Hindia. 261 



But that is merely shifting the argument away from the 

 proper and only path. Rcemer regarded the casts, which 

 he described very well, as those of a Favositoid coral, and 

 Dr. Hinde states in a footnote that " Ferd. Eoemer does not 

 stand alone in making this mistake." There is no possibility 

 of a zoologist classifying a lithistid sponge with Rcemer's 

 species by following his descriptions. Dr. Hinde, knowing 

 that the fossils erroneously described by Roemer are casts of 

 a lithistid sponge, has added to our knowledge ; but Koemer 

 was not aware of the fact, and did not state it. I do not see 

 that Dr. Hinde has improved his position, and in fact he 

 shows that Eoemer had not seen the form in any other state 

 ot preservation than that of a cast ; and we have yet to learn, 

 as paleeontologists, that the correct delineation and slight 

 description of a cast is to be accepted as a correct and useful 

 specific diagnosis of the perfect form. 



Fossil sponges are described according to their shape, the 

 shape and arrangement of their spicules, and the nature of 

 their outer (if there are any) and inner spicular elements ; but 

 Eoemer, whilst he noted the shape of the species, wrote nothing 

 about spicules or their arrangement ; he knew nothing about 

 them, and did not describe the species ^^ fibrosa " as the cast 

 of a sponge. He considered the form to belong to a species 

 already described by Goldfuss. 



The following is his description (Die Silur. Fauna d. 

 westl. Tennessee, p. 20, pi. ii. figs. 2, 2 a, I) : — 



^^ Calamopor a fibrosa, Goldfuss, Petref. Germ. i. p. 82, 

 t. xxviii. figs. 3 et 4, p. 215, t. Ixiv. fig. 9. 

 ^'Favosites fibrosa^ Lonsdale. 



" Zollgrosse, kugelige Massen, welche auf der ganzen Ober- 

 flache, mit sehr kleinen unregelmassig polygonalen unmittelbar 

 an einander stossenden Zellen-Miindungen bedeckt sind und 

 im innern aus sehr regelmassig von dem Mittelpunkte nach 

 Aussen grade und stratf austrahlenden und nach Aussen sich 

 verdickenden prismatischen haarformig diinnen Eohrenzellen 

 bestehen. Es ist mir nicht zweifellos ob die Stlicke wirklich 

 der Goldfuss'schen Art angehoren." 



The genus Hindia and its species were thus described by 

 me (Ann. & Mag. Nat. Hist. July 1879, p. 91) :— 



" Genus Hindia. 



" The body is free, without an involution of the texture, 

 and consists of a small central space occupied by spicules 



