9S 



A. " Jamesoni-bed," we shall mention with the Gr3rphsea of the marlstone 



series. 



Chapuis and Dewalque, in their "Description desFossiles des Terrains 

 Secondaires de Luxembourg," consider the following to be Synonymes of 

 Ostrea irregularis of Miinster in Goldfiiss, " 1835, Petrefacten, plate 79, 

 figure 5," which they adopt as occurring in the " Sable et Gr^s de 

 Martinsart," and the " Mame de Jamoigne," (the first and second stages 

 of their inferior lias,) which corresponds nearly enough vrith its strati- 

 graphical position in other localities, and consequently admits the 

 application of the observations of Oppel and Quenstedt, already cited, 

 in which it is treated as merely a variety of G. incurva, of 



Ostrea Laeviuscula Miinster, fig. 6, plate 79 ; 



O. ungula Miinster, 1835, Handbuch, 325, (jeune) ; 



O. semicircularis Roemer, 1836, plate 3, fig. 6 ; 



O. irregularis, D'Orbigny, 1850, Prod. t. 1, p. 238; 



O. intermedia Terquem, (MS.) 1853. 



Lycett, with regard to the Gryphaea Buckmani, in our transactions, 

 remarks — "The adherent species will be found to exhibit greater 

 variability than the others ; it may consequently be inferred that the 

 form is connected with a position which was accidentally attained by 

 variation of the attached shell."* 



It is useless to make fiirther references to published descriptions of 

 this oyster-like form, as most recent authorities coincide with the 

 opinions wliich are here stated, and which derive additional support 

 from a fact made known to us, since the commencement of these pages 

 by an observer upon whose trustworthiness we can safely rely, Mr. 

 Tomes, of Welford Hill, viz. that a perfect Gryphite form with the sheU, 

 well preserved, closely resembling young specimens of the G. obliqua 

 or rather G. Maccullochii varieties, occurs in the White Lias of 

 Bridgend, Glamorganshire, Figures 5, 6*, 5\ Plate 1, proving most 



• Goldfiias, at the conclusion of his descriptions of Gryphites, makes the following 

 observatioBS : — 



" It is evident, that in the Gryphites of the Liassic formation only, are combined those 

 characters by which they can be distingaished as species from Oysters. Indeed, in thoso 

 of the Oolitic formation, their near relationship to the Oysters is plainly shown ; and in the 

 Cretaceous, as well as in the Tertiary formations, are fonnd several kinds, in the individuals 

 of which the presence or the absence of the distinguishing character of Gryphites, appear to 

 be attributable merely to accidental variations of form, for this reason, both Ostrea truncata 

 and Gryphaea navicularis, are sometimes considered Oysters, sometimes Gryphites." 



In reference to Ostrea vesicnlaris, tab. 81, fig. 2, a to p, from the Chalk, the young 

 form of it, as there shown, is precisely that of a Gryphite, whilst with age it assumes 

 the expanded, flattened form of the Oyster; he also remarks, that — 



" Count Miinster distinguishes from G. truncata (tab. 81, fig. 2, c, g. f,) the broad thiu 

 individuals with striated and flat upper shells, as Ostrea vesicuiarii, (tab. 81, fig. 3, a, b, c,) 

 the first named, in fact, frequently assuming the narrow boat-shaped form of G. arcuata." 

 So interminable is the variety of which the entire family is susceptible. 



