48 BRITISH FOSSIL CORALS. 



very slightly flexuous, and presenting laterally a few large granulations. Dissepiments 

 simple, almost horizontal, and few in number ; about three from the top to the bottom of 

 each principal septum, as may be seen by means of a vertical section. Height varying 

 from one to two inches ; diameter of the calice, four lines ; depth of the fossula, two lines. 



The genus Parasmilia, circumscribed within the limits assigned to it in the Introduction 

 to this Monograph, only contains seven species, all of which belong exclusively to the upper 

 beds of the Chalk Formations. Three of them {P. centralis, P. Gravesiana, and P. elongatd) 

 have already been described in our Monograph of the Astreidae, 1 and the four others 

 (P. Mantellii, P. Fittonii, P. cylindrica, and P. serpentina) will be made known in the 

 present work. They all differ but little from each other, and in order to recognise them, 

 it is necessary that they should be compared together with attention. P. centralis, which 

 may be considered as the type of this small generic group, differs from P. Gravesiana, 

 P. elongata, P. cylindrica, and P. Mantellii, by its costae being always straight, rather 

 thick and never sub-lamellous, and rather flexuous, as in the four last-mentioned species ; it 

 is also to be remarked, that its costae are rather more prominent near the basis than higher 

 up, whereas the contrary is seen in the P. Gravesiana, and that the loculi are neveT 

 subdivided by small dissepiments, as is the case in P. elongata, P. cylindrica, and 

 P. Mantellii. P. serpentina, which bears more resemblance to it, is characterised by the 

 septa forming only three cycla, and the costae being very delicate, and rather indistinct 

 towards the basis. But it is with P. Fittonii that P. centralis is most closely allied ; the 

 former, however, is of a thicker form, its tertiary costae are more developed and more 

 delicately granulated, and its columella is much larger, and terminated by a sub-papillose 

 surface. 



The specimens of P. centralis which we had the opportunity of examining were found 

 in the Upper Chalk at Northfleet, near Gravesend, and at Norwich. Mr. Phillips mentions 

 the existence of the same fossil at Dane's Dike; 2 and Dr. Mantell has met with it at 

 Brighton, Lewes, 3 Steyning, and Heytesbury. 4 Mr. Graves also alludes to it as being 

 found in the Chalk Formation of the Parisian basin at Beauvais ; 5 but we have much reason 

 to think that the species observed by that geologist is not the one here described, and must 

 be referred to our P. Gravesiana. M. Rcemer and other authors equally apply the name 

 of C. centralis* to a fossil found in the north-west of Germany, but we have not been able 

 as yet to verify the propriety of this determination, not having seen any of the specimens 

 discovered in that part of the Continent 



1 The species described in that work under the names of Parasmilia poculum, P. Faujasii, and 

 P. punctata, must now be referred to our genus Coelosmilia, which is characterised by the entire absence of 

 the columella. 



3 Op. cit., parti, p. 119. 3 Illust. of the Geol. of Sussex, p. 160. 



4 Geol. Trans., 2d series, vol. iii, p. 204. 5 Geogn. de l'Oise, p. 701. 

 6 Versteinerungen des Norddeutschen Kreidebirges, p. 26. 



