E. F. Tomes— Corals of Cricldey Bill 303 



The type is T. patellata, E. de From. etTery, Paleont. Franc. 

 Terr. Juras. pi. 58, fig. 2 (1869). From the Middle Lias. 



The description of the genus appears in the Palseont. Franc. Terr. 

 Cretacee, p. 367. 



Thecoseris polymokpha, n.s. 



Corallum simple, variable in form, but always more or less tur- 

 binate, and non-attached. 



The wall is thin, its superior margin prominent, undulating and 

 sometimes almost foliaceous. 



Costse, when exposed by abrasion of the epitheca, numerous, 

 delicate, and with lateral synapticulge feebly developed. 



Epitheca thick, rugose, and exhibiting distinct rings of growth. 



Calice shallow, concave, and extremely variable in outline. Fossula 

 small, but round and well defined. 



Septa rather numerous, somewhat flexuous, irregular in thickness, 

 and not diminishing as they approach the calicular fossula. Those 

 of the younger cycles pass into those of the older ones. 



Synapticulge feebly developed. 



Height of the corallum ^ to 1^ inches. Diameter of the calice 1 

 to 1-| inches. This appears to be a common species in the Coral- 

 bed at Crickley. 



The genus Thecoseris appears to be nearly related to TrocJioseris, 

 but difi"ers most essentially from it in having no columella. In this 

 respect it resembles the genus Turhinoseris as defined by Prof. Duncan.^ 

 In the only example appertaining to this latter genus which I have 

 been able to examine (a specimen of Turhinoseris Be Fromenteli, 

 Duncan, from the Lower Greensand of Atherfield), the calice is a 

 little convex with a slightly everted margin, and with a shallow 

 round fossula. It bears very considerable resemblance to some 

 examples with unworn calicos, of Podoseris mamilliformis, Duncan, 

 from the Bed Chalk of Hunstanton,^ but it differs essentially in not 

 having any epitheca. The Podoseris mamilliformis is a particularly 

 variable species, as far as form is concerned, many specimens having 

 a turbinate form with a depressed calice, and a small but well- 

 marked central fossula. Yet all which I have examined (in number 

 considerably more than a hundred) have had a well-defined epitheca. 

 But the existence of an epitheca in this species is rendered less im- 

 portant in a generic point of view by the feeble degree of its develop- 

 ment in another species described by Dr. Duncan from the Oolite of 

 Dorsetshire, under the name of Podoseris constricta.^ Besides the 

 want of a well- developed epitheca, this species further departs from 

 the original definition of the genus Podoseris by having a small 

 instead of a large base. These peculiarities help to bring Podoseris 

 in nearer relationship with Turhinoseris : and with a more ample 

 list of species representing the genera Thecoseris, Podoseris, and 

 Turhinoseris, it is quite probable that they may require reconsidera- 

 tion. 



1 Supp. Brit. Fos. Cor. pt. ii. No. 2, p. 42 (1870). 



2 Supp. Brit. Fos. Cor. pt. ii. No. 1, p. 25 (1869). 



3 Supp. Brit. Fos. Cor. pt. iii. p. 24 (1872). 



