NEWTON: FOSSIL PEAKL-GEOWTHS. 135 



Inoceramus mytilloides, Mantell : Possils of the South Downs, or 

 Illustrations of the Geology of Sussex, 1822, p, 215, pi. xxviii, 

 fig- 2. 



This example is an interior of a left valve with well-preserved 

 shell-structure, on the surface of which is a sei'ies of small pearly- 

 tubercles, varying slightly in size, and situated chiefly on the anterior 

 surface and some distance from the hinge-line, being arranged more 

 or less concentrically as in the other shells previously mentioned. 



Although fragmentary, being without the postero- ventral region, 

 this specimen is important as showing the partial interior of an 

 Inoceramus valve, a condition of some rarity among members of that 

 genus. The early synonymy of the species may be thus explained : 

 Schlotheim founded his species lahiatus on a valve figured by Knorr 

 from the Pirna sandstone of Saxony. The name frohlematicus was 

 given subsequently by the same author for precisely the same shell, 

 and cannot therefore be retained. The Mantellian name of mytilloides 

 was established still later for a British form of Inoceramus which is 

 now generally acknowledged to be identical with the lahiatus of 

 Schlotheim, and therefore this latter name should be adopted. 



The species is a useful form from the horizonal point of view, being 

 characteristic of the Turonian division of the Upper Cretaceous rocks, 

 which includes that part of the ' Quaderstein ' of Germany containing 

 the Pirna sandstone, from whence Knorr's original specimen was 

 obtained. This particular valve has a length, of 70 mm. and a height 

 of 105 mm. 



Geological age. — Cretaceous (Turonian). 



Locality. — Blue Bell Hill, Burham, Kent. 



Collectio7i. —Bxiihh. Museum (S. J. Hawkins Coll.) [L. 10384]. 



Inoceramus. PI. IV, Fig. 5. 



Inoceramus, J. Morris: Ann. Mag. Nat. Hist., 1851, vol. viii, p. 89, 

 pi. iv, fig. 12. 



The example here referred to and refigured is the original as 

 described by John Morris. It represents a single rounded pearl 

 concretion attached by the whole of its base to a portion of an 

 Inoceramus shell. The various layers, being fractured in places, show 

 the exposed edges and their fibrous structure. This is a fairly large 

 relic of pearl-growth, and measures 1 3 mm. in diameter. 



Geological age. — Ci-etaceous (Senonian). 



Locality. — Northfleet, Kent. 



Collection.— '^x\ih\i Museum (IS". T. Wetherell Coll.) [L. 20845]. 



Inoceeamus. pi. V, Figs. 2, 3. 



This specimen consists of an elongate pearl-structure of pyriform 

 contour, longitudinally adherent to a fragment of Inoceramus shell. 

 It starts with being a rounded smooth body, and subsequently 

 developing a narrow, elongate extension on each side. A section of 

 this gives the concentric, radial structure in the rounded top of the 

 concretion, whereas the more fibrous character is observed in the 



