310 A New Species of Lima from the English Chalk. 



sphcera globularis Phillips, Ptychodus mammillaris Agassiz, 

 Oxyrhina mantelli Agassiz, and fish Vertebrae.* 



In the collection is a Lima remarkable alike for its unusual 

 shape and for its excellent state of preservation. It was found 

 in association with fossils typical of the base of the cor-anguinum 

 zone at a depth of about 70 feet from the ground-^vel. 



Fortunately, Mr. Henry Woods has published a monograph 

 on the Cretaceous Lamellibranchia, and his researches in 

 connexion with the Limidaef have considerably facilitated the 

 work of ascertaining that the present species had not been 

 previously described. 



Notwithstanding the extraordinary variations in form and 

 ornamentation in the species of Chalk Limidae figured and 

 described in this Monograph, the shape of the present specimen 

 is even more unusual than in any chalk Lima hitherto known. 

 The nearest related species is apparently Lima (Plagiostoma) 

 hoperi Mant., shown in figures 8a and 8b on Plate IV., of the 

 Monograph, from the zone of Actinocamax quadratus at East 

 Harnham, the specimen being in Dr. Blackmore's collection. 



The specimens of L. hoperi figured are not from the same 

 horizon as the Middleton quarry ; although we have a specimen 

 (a single valve) of L. hoperi from Middleton, but it is much 

 higher in comparison with its length than those figured by 

 Mr. Woods. 



Lima (Plagiostoma) middletonensis n.sp. 



The new species, to which we propose to give the name of 

 Lima {Plagiostoma) middletonensis, consists of two valves 

 preserved in contact near the umbones with the anterior dorsal 

 margins separated, and the ventral margins wide apart. The 

 left valve is quite perfect and the right valve has part of the 

 shell missing on the dorsal slope and towards the anterior 

 end. The following description therefore is based on an 

 examination of the left valve. 



Description : — Shell oval-oblong, nearly twice as long as 

 high, convex, rounded ; unusually inequilateral. Anterior- 

 dorsal margin very long, almost straight ; posterior-dorsal 

 margin very short ; the remainder forming a fairly regular 

 long-oval curve. Umbones pointed, close together. Apical 

 angle 125 . Ears small, with growth lines ; posterior longer 

 than high ; the left anterior ear broken, and the right not 

 well shown, but evidently smaller than the posterior ears. 

 Anterior area well developed and slightly concave, distinctly 



* In case any would-be collector is desirous of visiting the Middleton 

 Quarry, it may be as well to state that the owner's permission is necessary 

 before a visit can be made. 



f A Monograph of the Cretaceous Lamellibranchia of England. Mon. 

 Pal. Soc, Vol. II., Part 1, 1904, pp. 1-56. 



Naturalist, 



