NO. 14C1. G'ENERA OF SIMPLE FUNG ID CORALS— VAUGHAN. 397 



inentiil. In fact, tlie dissepiment.s are so arrantved as to give the 

 appearance of an imperforate wall in many, if not most, cases. Costse 

 present, representing- the peripheral ends of the septa; rather promi- 

 nent and distant, often with definite girdling exothecal rings, the dis- 

 sepiments in these rings extending to the costal ends. Between the 

 rings thinner dissepiments can often be seen. Septa irregularly per- 

 forate, the first and second cycles thicker and not so perforate as the 

 higher cycles, however they show distinct perforations; in three 

 polished sections I found about three thicker septa that seemed to be 

 imperforate. The septa of the higher cycles are thinner and more 

 l)erforate. There is no regularitj' in the perforations — they may 

 exist near the columella, in the median portion of a septum, or near 

 the peripheral (costal) end. A longitudinal section shows that the 

 trabecuhe may be interrupted. The septal pores do not fill up near 

 the base, probably due to the highly developed dissepiments cutting 

 ofi' the base of the corallum from the soft parts of the polyp. There 

 is a tendency, but not a very striking one, to form septal groups. 

 S^^napticula scarce, present near the base, and probably also near the 

 inner ends of the septa.. Dissepiments well developed, curving out- 

 ward, one set above another. In a cross section of a corallum they 

 show as several definite rings — usually three or four rings occur 

 between the columella and the peripheral or mural zone. Columella 

 distinctly developed, shows in transverse section as a number of axial 

 trabecule, which may be more or less fused among one another, and 

 to the inner ends of the septa. Its upper surface is probably, though 

 not positively, papillate. 



Type species. — Trochosnillia insl(/nts Duncan {—T. uislgnis Duncan 

 + T. arguta Duncan (not Reuss)), Quart. Jour. Geol. Soc. London, 

 XXIX, p. 552, pi. XIX, figs. 2, 2a; also tig. 3. 



Distribution. — Old Tertiaries of St. Bartholomew, West Indies. 



Remarl's. — How Duncan ever referred his Trocliosrn'dla insujuls to 

 Trochosmilld passes comprehension. As Prof. A. G. Hogbom, of the 

 Universit}^ of Upsala, has kindl}' loaned me Duncan's type, I have 

 been able to base a large portion of the above description on the type 

 specimen. Two thin sections, two polished transverse sections, and 

 one polished longitudinal section of other specimens were prepared. 

 Duncan's type (which had been cut) shows nearly ever}^ character, given 

 in the preceding diagnosis, that can be seen on a transverse section. 

 His figure of the transverse section (Plate xix, fig. 2a) clearh^ indi- 

 cates perforate septa. The specimen identified by Duncan as T. atyuta 

 Reuss is precisely the same thing. It also has perfectly distinct septal 

 perforations, and there are hints of columellar papillae 



This genus, I think, is most closeh' related to Freeh ia Gregory, but 

 can ])e inmiediately separated by its highly developed dissepiments. 

 The genus seems to bo unusually distinct from any of those previously 

 described. 



Proc. N. M. vol. xxviii— 04 26 



