27 



Habitat : — The unique Holotype was brought up in a deep-sea trawl at St. 2 1 i 

 (5°4o'.7S., i20°45'.5E., 1158 mètres). 



Remarks: — The sculpture of this species, which is restricted only to a quadrate area in 

 the middle of the shells, is very characteristic, and at once disting-uishes it from other species 

 of the sfenus. 



Ï3 



Genus Neilonella Dali. 



i88r. Neilonella (as a section oi Ledd) Dali, Bull. Mus. Comp. Zool. Harvard, IX, p. 125. 



1886. Neilonella Dali, Bull. Mus. Comp. Zool. Harvard, XII, p. 254. 



1897. Neilonella Verrill & Bush, Amer. Journ. Sci., (4) III, p. 57. 



1898. Neilonella Dali, Trans. Wagner Free Inst. Sci. Philadelphia, III, p. 582. 



Neilonella was proposed as a section of the g-enus Leda Schumacher (= NtLCulana Link), 

 but was later given generic rank and transferred to the subfamily Malletiinae. The génotype 

 is Neilonella corpulenta Dali. 



The four new species described below are assigned to this genus with some hésitation. 

 They correspond in ail characters to the définition of this genus of fossil forms, and in the 

 présent unsatisfactory condition of the nomenclature of the family I hâve referred them to Dall's 

 ofenus rather than introduce a new generic name. 



1. Neilonella djibia sp. nov. (Plate I, figs. 48, 49). 



The following is a description of this new species : — Shell of médium size, moderately 

 thick, subovate, tumid, inequilateral ; broadly rounded anteriorly, greatly narrowed posteriorly ; 

 subtruncate ; anterior dorsal slope obliquely slanting, posterior slope arched, concave; ventral 

 margin greatly arcuate ; umbones very prominent, tumid, strongly curved inwards and backwards ; 

 sculpture consisting of concentric, shallow low ridges ; posterior slope of valves almost smooth ; 

 hinge-plate strong, anterior séries with about 18 and posterior with 22 teeth separated by an 

 edentulous notch in middle; internai cartilage absent. Shell of olive yellow colour; nacre shining 

 bluish white. 



Measurements of Holotype: — Length 12 mm., height 7.5 mm., diameter 4.8mm. 



Habitat : — The Holotype with the left valve in fragments and a right valve were 

 brought up in a deep-sea trawl at St. 52 (9°3^4S., ii9°56'.7E., 959 mètres). 



2. Neilonella schepinani sp. nov. (Plate I, figs. 50, 51). 



The following is a description of this new species : — Shell of médium size, moderately 

 thick, donaciform, moderately tumid ; inequilateral ; narrowly rounded anteriorly ; greatly narrowed 

 and rounded posteriorly ; both anterior and posterior dorsal slopes straight, slanting ; ventral 

 margin greatly arcuate ; umbones smooth, acute, rounded, curved inwards and backwards ; sculpture 

 below the beak consisting of regular, concentric low ridges ; hinge-plate moderately strong, anterior 

 séries with about 12, posterior with 18 teeth. Shell of a pale straw colour; nacre shining white. 



Measurements of Holotype: — Length 6.5 mm., height 4.6mm., diameter 3.7mm. 



