SUBGENUS PRASOPORA. 203 



corallites are angular, and are furnished with numerous com- 

 plete, closely-set tabula;. The large tubes are prismatic, or 

 sometimes oval, Splniform corallites are wanting, or are 

 very sparingly developed {e.g., In Prasopoj^a Selwynii, NIch.) 

 The walls are thin, apparently structureless, and seemingly 

 amalgamated In adjoining tubes (though really not fused with 

 one another). Type of the group, Prasopora Graycs, NIch. 

 and Eth. jun. 



From those sections of Alonticulipoi'-a which have been here 

 distinguished under the names of Hetei^otrypa, Diplotrypa, and 

 Monotrypa, the species of Prasopora are at once separated by 

 the very peculiar nature of the tabulae of the large tubes. ^ In 

 this respect, Prasopora differs from all the Montlculfporolds 

 except the small group which I have Included In the succeed- 

 ing section Peroiiopora. From the species of this last-named 

 division, however, the Prasoporce are distinguished by the thin 

 and apparently structureless condition of the walls of the coral- 

 lites, by the absence or limited development of splniform 

 corallites, and by the constantly semi-globose or discoid form 

 of the corallum. 



The characters of Prasopora will be more fully brought out 

 In the descriptions of the following three species, comprising all 

 the forms which I am able at present to refer to this section. 



Monticulipora (Prasopora) Grayae, Nich. and Eth. jun. 



{Figs. 42 and 43.) 



Prasopora Grayce^ Nich. and Eth. jun., Ann. Nat. Hist., sen 4, vol. xx. 

 p. 392, 1877 ; Monograph Sil. Foss. Girvan, vol. i. p. 48. 



Spet. Char. — Corallum forming small hemispheric or concavo- 

 convex masses, from half an Inch to three-quarters of an Inch 

 In diameter, and from a quarter to half an Inch In height. 



1 Owing to an unfortunate intermixture of some of my microscopic sections, I 

 was formerly led to ascribe tabulae of this peculiar type to M. {Diplotrypa) IVkit- 

 eavesii, Nich. ; but this species, as previously shown, has really the complete tabular 

 which distinguish all the species of Diplotrypa. 



