48 KECENT MADREI'OKAHIA oK THK HAW.VIIAX ISLANDS AND LAYSAN. 



Yadmch there is not a oe'u.s that .lillVivntiatos it from the faunas of the South 

 I'ueili.-Indian Ocean ref,non. In fact, as has heen said, there has been only partial 

 .peeitie diHVrentiation between th.- two ar.'as. Tlie Hawaiian fauna, therefore, 

 shoukl he classed with the Southern I'aeilic-Indian Ocean fauna, and it probably was 

 derived from the latter at a .ompuratively recent date. 



The Hawaiian reef fauna exhibits a peeuliarity wortliy of furtlier notice, in the 

 absence of some of the eoninu.u reef-building uenera of other areas. There are no 

 species of the Oculinid;e. Eusniiliida-. or the Astrangiida-. tiuM-e are very few Orbi- 

 cellida^ none of the large, massive, mcandrinoid Faviida', nor of the Mussida;. The 

 genus Arropom is, possibly, but not i)robabiy, excepting .1. eehinata, entirely absent. 

 Dana" noted the absence or scarcity of these' corals about the Islands, and accounts 

 for it by their lying outside the torrid zone of oceanic temperature, in the subtorrid, 

 where the corals are eonse<inently less luxuriant and iiuuh fewer in species. Dana s 

 explanation may be correct, but it does not seem to be supported by sufficient evidence 

 to warrant its acceptance. Therefore, T should like to suggest an alternative expla- 

 nation. As is w(dl known, the species inhal)iting the waters of the Bermuda Islands 

 are all idiMitieal wilii AntiUean and Fhiridian speeies. No species of Acropora, 

 however, is found in Bermuda. The Bermudan is an emigrant fauna, and I have 

 suggested that the same is true of the Hawaiian. Is it not possible that the larvie 

 of some species and some genera can not be transported alive for great distances by 

 currents, whih^ others can be? 



SYSTEMATIC DISCUSSION OF THE P'AUNA. 



MADREPORARIA IMPERFORATA. 

 Family FLABELLID.E Bourne. 



1900. Flahdlhur (iuKciouY, .Jurassic Cor. of the Cutch, p. :'A. 



1905. Fhihellida: Boirne, Kov. Soc. Kept, on Pearl ()y.-<ter Fisheries, IV, p. 19.5. 



Tifpi'-yvn UH. — J'lahfll KM Lesson. 



Diii(/iio.yi-s. — Coralluui with imperforate tissues, simple or reproducing by gemma- 

 tion within the cu]), cuneiform or conical, originally with a small base, which is 

 attached in the early growth stages, but which subse((uently may be broken off. 



Wall coinpo.sed of an epitheea that is closely applied to the outer ends of the septa 

 and extends upward to the edge of the i-alice. Within tliis epithecal wall there may 

 be a solid deposit of stcreoplasm, which in some instances obliterates the interseptal 

 loculi in the basal portion of the coniUum. 



Septal margins entire. 



Hf'iiKii'Ii.s.-This family contains Rhhofi'ochux,'' Dinu'ania Pourtales, TLijjUo- 

 phyllia Pourtales, and Gdrdineria^ which is here described as a new genus. Accord- 

 ing to Bourne Placotrochus belongs here. 



oCorals and Coral Island, 3d ed., p,. 111. 



ftConsidered a .synonvm of Plahdhun by Cianliner, Marine Invest, in Soutli Africa, II. p. 117. 



