18 TROCHOSMILIDJE. 



circular wall arises from the floor and separates the interseptal 

 chamljers in two, the outer portion becoming the rootlike append- 

 age. The cavity of the roots opens freely into the interseptal 

 chambers (Plate XIY., fig. 3), and is occupied by a fibrous extension of 

 the polyp. In old specimens the cavity becomes much reduced 

 by the thickening of the walls. 



The color of the polyp is greenish, or pale brick-red. 



This coral was obtained in about forty different casts along the 

 Florida reef, the least depth in which it was found being 49 fathoms, 

 the greatest 324. The greatest abundance was between 100 and 

 200 fathoms. 



Height 2 to 2.8 cm., diameter of calicle 1.5 to 2 cm. 



TROCHOSMILID^. 



Trochosmiliacece M.-Edw. & H. 



For reasons elsewhere stated, I prefer to elevate this group to 

 the rank of a familv, instead of leavino- it amouo; the Astranda^ as 

 a mere section of the subfimily of Eusmilina^, the place assigned 

 to it by Milne-Edwards and Haime. Its affinities are j)artly 

 with the Astraiida? and partly with the Turbinolida?. We are not 

 sufficiently acquainted with the value of the characters connecting 

 it with either to say positively wdiich of them ought to have the 

 preponderance. As a family, it appears homogeneous, but the 

 order or suborder to which it ought to be attached can be left 

 undetermined for the present. 



The principal character by which to separate the Trochosmilida? 

 from the Turbinolida? is the presence in the former of dissepi- 

 ments closing the interseptal chambers. In a large number of 

 them they are of a very rudimentary character, and no more de- 

 veloped than the}^ are occasionally in true Caryophyllia^ where I 

 have observed similar structures secreted abnormally to exclude 

 parasites. 



The mode of propagation observed in three of the species here 

 described, namely, a gemmation from the interior of the calicle, recalls 

 the peculiar intracalicinar gemmation of the Rugosa, and does not 

 prevail among any of the families of corals of the present epoch. 



