234 MR. E. T. NEWTON ON MESOZOIC FOSSILS [May IpOI, 



these are common in the Lower Lias, and have been referred to 

 0. irregularis. This species has been recorded from the Ehaetic, as 

 well as from Ammonites angulatus- and Am.m. JSuchlandi-heds in 

 the Belfast district, and from the last two horizons in Yorkshire. 



Myoconcha psilonoti (?) Quenstedb. (PI. IX, fig. 10.) 



1858. ' Der Jura ' p. 48 & pi. iv, fig. 15. 



1870. Tate, ' Irish Liassic Fossils ' Eep. Belfast Nat. Field Club, App. i, p. 12, 



1876. Tate & Blake, ' Yorkshire Lias ' p. 393. 



The impression of the middle portion of a Myoconcha showing 

 the characteristic lines radiating" from the umbo, agrees, so far as 

 preserved, with M. psilonoti, which has been identified in the 

 Ammonites a^igulatus-heds of Antrim and Yorkshire and from Amm. 

 BveMa7idi-heds in the latter area. Mr. Horace B. Woodward ^ 

 notices the species from Ammonites planorhis -heds elsewhere in 

 England. 



jSTucula. sp. 



There are four or five internal easts of an oval Nucula, showino^ 

 hinge-teeth and with prominent umbones, which certainly belong to 

 this genus but may represent more than one species. 



IN'ucTjLANA (Leda) Tatei, Ncwton. (PI. IX, fig. 12.) 



1870. Leda Renevieri, Tate, ' Irish Liassic Fossils ' Eep. Belfast Nat. Field 

 Club, App. i, p. 19 & pi. i, fig. 3. 



1876. Leda Benevierei, Tate & Blake, ' Yorkshire Lias ' p. 384 & pi. xi, fig. 4. 



1858. Nucula complanata ^, Quenstedt, 'Der Jura' p. 110 & pi. xiii, fig. 40 

 {non fig. 39). 



1856. ? Leda tenuistriata, Piette, Bull. Soc. Geol. France, ser. 2, vol. xiii & pi. x, 

 fig. 4, p. 206. 



Non Leda JRenevieri, Oppel, 'Die Jurafoiination ' p. 95 (1856-58). 



This form was originally described by Prof. Tate from Irish 

 specimens, and was afterwards refigured in the ' Yorkshire Lias.' 

 In both localities it occurs in Ammonites angulatus- and Amm. 

 BucMandi-hed8. Tate's specimens are now in the Museum of 

 Practical Geology, and show that both the figures are from imperfect 

 specimens which must, when perfect, have had the rostrum longer 

 than would appear from either the figures or descriptions. The 

 upper margin of the rostrum is straight or slightly convex with, 

 external ridges, and it abuts against the umbones so sharply that it 

 forms a distinct angle. The under margin of the rostrum is concave. 

 These characters serve to separate the species from Nucula com- 

 jjlanata, Goldfuss, to which imperfect specimens bear a close 

 resemblance. Oppel states that the rostrum of his Leda Benevieri 

 is shorter than in Nucula complanata : this, it seems to me, prevents 

 the Irish specimens, figured by Prof. Tate, from being referred to the 

 same species, and Messrs. Tate & Blake (' Yorkshire Lias ' p. 384) 

 were evidently uncertain as to the use of the name Leda Benevieri. 

 This species is in all probability the form figured by Quenstedt 

 (op. cit. pi. xiii, fig. 40) as Nucula complanata (3. As a name is 

 wanted for this Leda, it may be called L. Tatei. 



^ Mem. Geol. Surv. 'Jurassic Eocks of Britain, vol. iii (1893) Lias of. 

 England & Wales ' p. S59. 



