On new Species of IHsteiidfe. 95 



Wealden fossil just described to prevent its reference to an 

 Elopine or Clupeoid fish ; but as the European Wealdeu 

 fish-fauna is essentially of a Jurassic type*, the specimen is 

 more likely to belong to a member of the Leptole])ida3, with 

 which it equally agrees. The skeleton of the trunk resembles 

 that both of Leptolepis itself and of JEthalion ; but the lack 

 of jaws prevents an exact determination of the genus. The 

 number of the vertebrte exceeds that of all known species of 

 both genera except zEtlialion Vidali-\, and the relative short- 

 ness of the hinder caudal, as well as the anterior abdominal 

 vertebral centra, is a feature peculiar to the new Wealdeu 

 fish. The tins, as described, also distinguish this fossil from 

 all species with which it can be compared. It therefore 

 represents a new species^ which I propose to name Leptolepis 

 valdensis until the discovery of the head determines its 

 precise generic position. 



EXPLANATION OF PLATE I. 



Fi<j. \ . Leptoli'ins valdensis, sp. u. ; rig'lit side view of type specimen, one 

 lialt'iiiit. size. — Weald Clay; Southwater, Sussex. [Bi'it. Mus. 

 no. P. 10440.] a., anal lin ; hr., branchios^egal rays ; c, caudal 

 fin ; cl., clavicle ; d., dorsal fin ; km., hyomandibular ; np.^ oper- 

 culum ; plv., pelvic tins ; p»p., preoperculum ; pt,^ post-temporal ; 

 •se/., supraclavicle ; sop., suboperculum. 



Fuj. 2. Ditto ; caudal vertebra3 of same specimeu, nat. size. 



XVIII. — On nexo Species o/HisteridfB and Notices of others. 

 ]^y G. Lewis, F.L.S. 



This is the thirty-first paper of this series, which dat'^s from 

 the year 1884. Jn the liisteridaj the absence or otherwise of 

 prosternal striaj is sometimes of great significance, and servos 

 to distinguish both genera and species. Thus, in Teretrio- 

 soma the striaj are wanting, in Terefrius they are well mai-kijd 

 and very useful as specific characters; and in Paromalus, as 

 the genus is now defined, the prosternal keel is marginate — 

 that is, the stri* meet at both ends. In Grammostethus^ 

 also, the ])rosternal stride are of importance, as being con- 

 stantly similar in a series of fourteen cognate species, but 

 which possess, however, inter alia^ good specific characters. 



* A. S. Woodward, " Note on the Affinities of the English Wealden 

 Fish Fauna," Geol. Mag. [4] vol. iii. (189C) pp. G9-7L 



t n. E. Sauvage, " Noticia sobre los Peces de la Caliza litograllca de 

 la Provincin de Lerida," .Mem. K. Acad. Cienc. Barcelona, [yj vol. iv. 

 no. 3o (lij03), p. ly, pi. ii. fig. 2. 



