144 THREE CRUISES OF THE " BLAKE." 



deposits, this fact would go far towards settling the question of 

 the depths of the cretaceous sea. Along the coast range of 

 Chili, in the nitrate districts, the position of the flint beds shows 

 that they were deposited in estuaries. Judging by the analogy 

 of their recent representatives, the siliceous sponges so common 

 in many of the formations must have lived at considerable 

 depths. The presence of pentacrinoids and their allies, which 

 were not attached to the bottom, but like those of to-day lived 

 imbedded in mud or ooze, denotes deep water ; while fossil 

 types with a strong, powerful root may give evidence of shal- 

 lower waters. 



Were we to decide by the size of the fossils, the smallness of 

 the mollusks and echinoderms collected from certain beds, like 

 those of the triassic beds of St. Cassian, would point to a deep- 

 sea fauna. 



The liassic beds of Hierlatz near Hallstadt in Austria are said 

 by Fuchs to be analogous perhaps to massive calcareous de- 

 posits hke the Pourtales Plateau of Florida. Massive whitish, 

 subcrystalline limestone occurs in them, built up almost entirely 

 of small brachiopods ; but deep-sea corals are wanting in these 

 beds. 



Many of the cephalopods of to-day are like the argonaut, pe- 

 lagic, or else they are deep-sea types, like nautilus and spirula. 

 The Eryon-like Crustacea brought up by the dredge are all in- 

 habitants of considerable dej^ths, and the macruroids, Ophidiidse, 

 and the like, are deep-water fishes. We should constantly bear 

 in mind that the absence of certain types of invertebrates may 

 be very marked, owing to the disappearance of the more sol- 

 uble tests from beds in which the heavier and less soluble 

 remains are still to be found. So that in many formations 

 we probably find only a part of the fauna which, when in its 

 most flourishingf condition must have characterized them. The 

 fauna of the deposits of the old red sandstone of the Connecti- 

 cut River indicates that it lived in shallow water, while de- 

 posits rich in remains of belemnites, etc., were formed in deep 

 waters. 



The scarcity of vertebrate bones in dredgings is very marked. 

 Mr. Pourtales, who seems to have been more fortunate than all 



