56 CRETACEOUS LAMELLTBRANCHIA. 



smaller than elsewhere, but the middle rows of spines are here often relatively 

 larger. 



Measurements : 



(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (LI) 



Length 19 16 15 11 10 10 10 8 9-5 16 21 mm. 

 Height 21 18 16 12%5 11 10'5 11 9 10 18 ?24 „ 



(1 — 5) B. mucronata zone, Norwich. 



(6) ,, „ Alderbury. 



(7) A. quadratus zone, East Harnham. 



(8) B. mucronata zone, Clarendon. 

 (9—11) Chalk of Trimingham. 



Affinities. — The form from the Lower Senonian of Touraine described and figured 

 as Lima granulata by Dujardin, is regarded by Peron ' as belonging to another 

 species which he names Lima Meslei. Peron states that L. Meslei differs from L. 

 granulata in having more numerous ribs ornamented with fine granules of which 

 the middle row is not larger than the lateral rows ; further, the ribs disappear on 

 the anterior and posterior parts of the shell, and the ears are without ornamen- 

 tation. 



Badula scabricula, Stoliczka, 2 from the Arrialoor Group, is closely related to 

 Lima granulata, but owing to the imperfect preservation of the single valve on 

 which the species is founded, an exact comparison is not possible. The ornamen- 

 tation, however, seems to differ, since it apparently consists of small tubercles of 

 nearly equal size. It has been suggested by Holzapfel and Hennig that Lima 

 jjseudocardium, Reuss, 3 may be identical with L. granulata, but the ornamentation 

 on the ribs of that species appears to be unknown. 



Remarks. — This species has been referred to Limca by Brauns, Zittel, and 

 Grriepenkerl, but later writers — Holzapfel, Hennig, and Ravn — retain it in the 

 genus Lima since they find no evidence of the existence of a taxodont hinge. 

 The specimens which I have seen do not show the hinge. 



The outline of the shell varies to some extent in L. granulata, depending mainly 

 on the obliquity of the valves. The appearance of the ribs varies considerably and 

 is probably due chiefly to the state of preservation ; in the more perfect specimens 

 the terminations of the scale-like spines become erect, in others the spines are 

 in the form of sloping scales, whilst in some cases they are represented by 

 tubercles only. The number of ribs also shows variation. 



1 ' L'Hist. du Terr, de Craie' (1888), p. 148, pi. i, figs. 21—24. 



2 ' Palseont. Indica, Cret. Fauna S. India' (1871), vol. iii, p. 419, pi. xxx, fig. 8. 



3 ' Die Verstein. der bohm. Ki-eideformat.' (1846), pt. 2, p. 33, pi. xxxviii, figs. 2, 3 ; Geinitz, 

 "Das Elbthalgeb. in Sachsen " (' Palaeontographica,' vol. xx, pt. 1, 1872), p. 204, pi. xlii, figs. 14, 15 : 

 see also Brauns (1876), Fritsch (1877, 1883), Michael (1893), Leonhard (1897). 



