Bibliographical Notices. 269 



in detail with Zittel's " Monactinellidae " — that is, sponges which 

 consist only of " spicules which possess a single unbranched interior 

 canal," which, so long as the monactinellid has a peculiar feature, 

 answers very well for identification ; but when the spicule is a 

 simple acerate — that is, linear, more or less curved (for if looked 

 at in a favourable direction it is seldom otherwise), fusiform, gradu- 

 ally sharp -pointed, and smooth, as in pi. i. figs. 1-3, — the power of 

 the term continues for the spicule, but ends for that of distinction 

 of species ; for this form is perhaps of all the most common, and 

 extends to totally different families. Mr. Hinde has evidently ex- 

 perienced this difficulty. 



Again, tho " Tctractinellidaj " of Marshall, characterized by 

 spicules with " four arms or rays, one usually much longer than the 

 ethers, radiating from a centre " (p. 24), might do for the Pachy- 

 tragida (Carter), but no other sponges. 8o the " Siliceous Globules " 

 (p. 38) may belong to Placospongia melubesioides, Gray, whose 

 skeleton-spicules are pin-like, with the points outwards, thus, 

 with other concomitants, allying itself to the Suberitida (Carter). 

 The " Quadrifid Spicules of Pachastrella " are less open to difficulty 

 in this respect ; while the fully formed spicules of Zittel's " Mega- 

 merina" and " Tetracladina" (Lithistina), and those of the order 

 " Hexactinellidge (0. Schmidt)," are self-evident, both recent and 

 fossil, as well as the incomplete ones of the former (pi. iv. figs. 2-4-34), 

 which we now know to be only a transitionary state of the disk to the 

 ulterior development of the Lithistid spicule. Here it is that Prof. 

 Zittel, by his sagacity, success, and indefatigable labours both at 

 home and in the field, has so enriched the Palajontological Museum 

 of Munich — which, together with his numerous discoveries, quite 

 marks an epoch in the early history of the Spongida ; while the 

 exquisite beauty of the fossil remains he has collected, once seen 

 and begun to be studied, is so fascinating as to recall to mind the 

 saying " Vestigia nulla retrorsum." 



Lastly, Mr. Hinde alludes to the destruction of the spicule, ob- 

 serving that " the peculiar form of the perforations (in the fossil 

 spicule) shows that they have been produced by the action of 

 some living organism," but different from that of Duncan's Palce- 

 acUya perforans. 



iiaving gone through all the sponge-spicules of the " paramoudra" 

 both descriptively and comparatively, not only with reference to the 

 recent but the fossil sponge-spicules also, that have been made known, 

 Mr, Hinde adds a most interesting " Summary " of his results, 

 which must be read in extenso to be properly appreciated ; nor can 

 we fail to notice in the " Postscript " that desire to which we 

 alluded in the beginning, viz. not to create new genera or species 

 before making himself acquainted with what has already been pub- 

 lished on both fossil and recent sponges. 



Finally, we would observe that, with such principles and oppor- 

 tunities, under the able and willing guidance of Prof. Zittel, it is 

 hardly necessary to add that Mr. Hinde's " Inaugural Dissertation " 

 tells us most satisfactorily the state of sponge-development at the 

 time the Upper Chalk was deposited. 



