and old age, being overgrown by the same parasites,* which, like 

 them, have succumbed to the changes of the conditions of existence 

 common to all of them, and differ from their predecessors, only in 

 diminished proportions. Both the assumed adult forms before referred 

 to, G. incurva and obliqua, occur sparingly in the A. oxynotus beds, 

 whilst the young form here exhibited. Figures 2, 3, and 4, Plate 3, is 

 very common, and is doubtless that, which at a more advanced age, 

 has received the name of G. suilla, to which we shall have occasion 

 hereafter to more particularly refer. 



The next four specimens produced are from beds still higher in the 

 series, in the group which probably represents the Ammonites rari- 

 costatus zone of Oppel, well exposed in " Skirts' cutting" on the 

 Oxford, Worcester, and Wolverhampton Railway. Fig. 2, 2*, 2^, 

 Plate 4, is from " Skirts' cutting," where it occurs with Ammonites 

 planicostatus and Hippopodium. Figure 3, Plate 4, is from the 

 Hippopodium bed, described by Mr. Gavey in the Quarterly Journal 

 of the Geological Society, associated with Ammonites raricostatus. 



Figure 2 being evidently a half-grown form closely resembling 

 the variety Figures 1, 1*, I'', Plate 4, intermediate to G. Mac- 

 cullochii and cymbium last figured, it is worthy of notice that while 

 Figure 3, Plate 4, approaches very nearly in outline to Goldfuss's 

 figure of G. cymbium, Plate 85, Figure 1, Fig. 4, Plate 4, re-assures 

 us that we have still before us Gryphaea incurva. It has become 

 more elongated in proportion to its width, but preserves every other 

 character ; while Figs. 2 and 3, making allowance for dissimilarity of 

 age, differ from it only in having lost almost every trace of the lateral 

 furrow. Closely associated with these forms, differing only in the 

 same degree as Gryphaea, Var. striata of Goldfuss, from Grypliasa 

 incurva rugosa, is the specimen represented by Figures 2, 2% 2^, 

 Plate 5, which still more nearly approximates to Gryphaea cym- 

 bium, before mentioned. This specimen, which is the only one we 

 have seen from the stratum in which it was found, is from the zone 

 of Ammonites Henleyi, and may be considered to be the last 

 appearance of what we believe to be any variety of G. incurva in 

 the lower lias, unless Figures 3, 3*, 3^, Plate 5, from a specimen lent 

 us by the Council of the Worcester Naturalists' Society, deposited 

 in its Museum by Mr. Gavey, without naming the locality from which 

 it was derived, should prove to be, as is probable, from the Ammonites 

 Ibex beds of Mickleton, which would bring us almost to the base of 

 the middle lias. These specimens agree perfectly with those figured 



* Anomia: aud Serpula;. 



