326 



NATURE 



\Angjist 16, 1877 



A glance at the above list, and, much more, an inspection of 

 the chalk mollusca in a good collection, ought to convince any 

 conchologist that all these genera were comparatively shallow- 

 water forms. I should infer that the depth might have been 

 from low-water mark to 40 or 50 fathoms. None of the penera 

 are deep-water. Chania, Oslrca, Pinna, Calyptnra, Hipponyx, 

 and, most assuredly, Patella cannot be placed m the latter 

 category ; and the old proverb, "noscitur ex sociis," will apply 

 to mollusks as well as to men. Teredo may have been littoral or 

 have come from floating wood. Not a single species of Leda^ 

 Pecehiolia (or Verticordia), A'eu-ra, not one of the Solenoconchia, 

 nor of the Bulla family occurs in the upper or white chalk, 

 although they now inhabit the deep-sea ooze and especially 

 characterize the modern deposit. 



Hut .Vaulilics and Spirilla are believed by some to be deep- 

 water forms. This must be a mistake. Although the animal of 

 that common species Nautilus pempiliiis has rarely been met 

 with, the shells are often found on beaches in the Indian Ocean 

 and South Pacific ; and I am not aware of any instance of a 

 deep-water moUusk being cast ashore. It is not likely. Rum- 

 phius (the " Plinius Indicus"), in his " Amboinsche Rariteit- 

 kamer," or Cabinet of the Curiosities of Amboyna, 1705, has 

 given an interesting account of the habits of the pearly nautilus, 

 a translation of which I will copy from the admirable monograph 

 of Professor Owen : — " When the nautilus floats on the water, 

 he puts out his head and all his tentacles, and spreads them upon 

 the water, with the poop of the shell above water ; but at the 

 bottom he creeps in the reverse position, with his boat above 

 him, and with his head and tentacles upon the ground, making 

 a tolerably quick progress. He keeps himself chiefly upon the 

 ground, creeping also sometimes into the nets of the fishermen ; 

 but after a storm, as the weather becomes calm, they are seen in 

 troops, floating on the water, being driven up by the agitation of 

 the waves. This sailing, however, is not of long continuance, 

 for having taken in all their tentacles, they upset their boat, and 

 so return to the bottom." 



As to the Spirilla, the old Dutch naturalist'Temarked that it 

 attaches itself to the rocks, and is thrown up on the beach when 

 the north wind blows. I'eron found the first living specimen in 

 Australia ; Mr. Percy Earl obtained one on the coast of New 

 Zealand ; the late Sir Edward Belcher another in the Indian 

 Archipelago ; Mr. Bennett got one off Timor ; and an imperfect 

 specimen was procured in the Challenger Expedition. 1 was 

 favoured, in January, 1875, t>y ^''- J- Tyerman, of Trcgeny, 

 sending for my inspection a perfect specimen of Spirilla auslralis 

 and one of Ars^onaiila gondola in spirit of wine, with a memo- 

 randum that "the Spirilla and Argonauta were taken by a friend 

 while dredging or, rather, skimming for pteropods in the Persian 

 Gulf." Mr. Tyerman added that other live specimens of the 

 Spirilla were captured at the same time. Sir Lewis Pelly informs 

 me that the Persian Gulf is nowhere deeper than between 40 and 

 50 fathoms. Spirilla has apparently the same habit as species 

 of Loligo and .allied genera, in occasionally frequenting the 

 surface of the sea. The shells of S. australis are thrown up in 

 considerable numbers on every beach in the North Atlantic, 

 having been wafted northwards by winds and the equatorial 

 current or so-called **Gulf Stream." 



Assuming, therefore, that the usual habitat of mollusca in 

 past epochs did not differ from that of recent mollusca of the 

 same kind, I think we may safely conclude that the shells of the 

 cretaceous system, or, more strictly, the upper chalk, belonged 

 to shallow and not deep-water mollusca. 



Mr. Woodward tells me that the chalk Crustacea are also 

 shallow-water forms. 



The white chalk is in many places principally composed of 

 GltibigeriiuT, Orbuliiue, and coccoliths or coccospheres, all of 

 which inhabit at present the surface of the sea. According to 

 Dr. Wallich, Globigerina is found in all latitudes and at all 

 depths, ranging from 50 to 3,000 fathoms.' Mr. Parker and 

 Prof. Rupert Jones (first-rate authorities on the foraminifera) 

 admit that Orbidina undGlobigerina are " occasionally found in 

 shallow water." - 



1 cannot identify a single species of the cretaceous mollusca 

 as now living or recent. All of them are evidently tropical 

 forms. One of the cretaceous species, indeed, Terebraliila 

 striata, Wahlenberg, has been supposed by some paLi.'ontologists 

 to be identical with T. caput-scrpentis, the latter of which has a 

 range of bathymetrical distribution from low-water mark to 



* " North-Atlantic Sea-bed." p. 137. 



- Quart. Joitni. Geol. Soc, vol. .\vi. p. 279. 



