276 Reviews — Subsidence of Reef -encircled Islands. 



II. — Subsidence of Reef-encircled Islands. By W. M. Davis. 

 Ball. Geol. Soc. Amer., vol. xxix, pp. 489-574, 1918. 



SINCE the preceding review was written, another and much 

 longer paper of earlier date has come to hand, in which 

 Professor Davis enunciates in greater detail, with more numerous 

 figures, the views summarized ahove. He also pays more attention 

 to the negative evidence, as shown by the absence of reefs on coasts 

 of emergence or in areas where their growth is prevented by 

 accumulation of detrital deposits on a large scale. The reefless 

 coast of Madras, which has risen from the sea, is contrasted with the 

 half-submerged cliffs of the north-east side of New Caledonia, now 

 bordered by fringing reefs, with a barrier reef 5 to 10 miles off 

 the shore. Stress is also laid on the unequal depths of lagoons 

 and banks, which are inconsistent with the requirements of the 

 glacial control theory, and several pages are devoted to a discussion 

 of the origin of atolls. The conclusions to be drawn from the 

 Funafuti and Bermuda borings are briefly summarized, and it is 

 pointed out that information as to the depth of atoll-lagoons is still 

 far from complete. Professor Davis believes that Darwin's theory 

 of intermittent subsidence affords the most satisfactory explanation 

 of atolls as well as for the other types of reef. He also considers 

 that Molengraafs theory of volcanic subsidence, while not proved 

 to demonstration, is a contribution of much value to the solution 

 of the reef problem. An extensive bibliography is appended to 

 the paper. 



III. — The Antiquity of Parasitic Disease. 



On the Parasitism of Carboniferous Crinoids. By Bor L. Hoodie. 

 Journ. Parasitology, iv, pp. 174-6. June, 1918. 



MR. MOODIE means "parasitism on crinoids" or what our 

 scientist-stylists would call "the parasitization of crinoids". 

 He has found in America (North or South ; locality not given) in 

 some Carboniferous rocks of age not stated (though Keokuk is alluded 

 to), crinoid stems swollen in reaction to the attacks of a parasite, 

 similar to those described by R. Etheridge fil. (1879, Proc^ Nat. Hist. 

 Soc. Glasgow, iv, pp. 19-36). Mr. Etheridge quoted descriptions by 

 previous authors, but was the first to assign the phenomena to their 

 true cause, and (pace Mr. Moodie) to determine the parasites in 

 several instances. Yon Graff (1885) compared these swellings, as 

 well as others in Mesozoic crinoids, to those due in recent crinoids 

 to the attacks of Jlyzostoma, but he did not prove this by any 

 discovery " of " the carbonized remains of" a myzostomid, as 

 Mr. Moodie states. Mr. Moodie claims that the stems at his 

 " disposal are the first to be recognized in America as in many ways 

 suggesting parasitism ". He should look at Wachsmuth & Springer's 

 Crinoidea Camerata of North America (1897), p. 43, pi. i, fig. 2; 

 also p. 502, pi. xxxix, fig. 7, which shows swellings on the arms of 

 an Agaricocrinus much more like myzostomid cysts than anything 

 figured by Von Graff. 



