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. elongata) 
have already been described in our Monograph of the Astreidee,t and the four others 
(P. Mantellii, P. Fitton, 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 costee 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 costa are rather more prominent near the basis than higher 
up, whereas the contrary is seen in the P. Gravesiana, and that the loculi are never 
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 coste being very delicate, and rather indistinct 
towards the basis. But it is with P. Métonii 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;? and Dr. Mantell has met with it at 
Brighton, Lewes,* Steynmg, and Heytesbury.* Mr. Graves also alludes to it as being 
found in the Chalk Formation of the Parisian basin at Beauvais ;? 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. Reemer 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. 
' The species described in that work under the names of Parasmilia poculum, P. Faujasii, and 
P. punctata, must now be referred to our genus Celosmilia, which is characterised by the entire absence of 
the columella. 
2 Op. cit., parti, p. 119. 5 Illust. of the Geol. of Sussex, p. 160. 
* Geol. Trans., 2d series, vol. iii, p. 204. 5 Geogn. de I’Oise, p. 701. 
® Versteimerungen des Norddeutschen Kreidebirges, p. 26. 
