252 NOTEfl ON THE TERMIAN SYSTEM OF 



any one may ascertain by consulting the figures and descriptions 

 given by both these authors in the " Versteinerungen" and 

 " Monograph." 



Stroph. Goldfassi, Mlinst., is thus characterised by Geinitz : — 

 " Back (ventral) shell roundish oval, quite like the preceding 

 species (0. lamellosus, Gein.), and also without a sinus, and 

 covered all over the surface with close-set tubular spines, and 

 with a short but high area," The shells figured by Mr. King, 

 Mon. tab. 12, figs. 13, 14, 15, 16, so evidently belong to the 

 above description, that I need not quote Geinitz further to prove 

 it. This is the form which I formerly described as Productus 

 aspeiTimus. 



Geinitz's 0. excavatiis is described as hemispherical tranverse- 

 oval, with a small, depressed, pointed umbo, a high area, and a 

 narrow, sometimes only weakly-marked sinus, with fine concen- 

 tric striae, and studded with thin but long tubular spines. The 

 general character, "halbkugelig quer-oval," is so expressive of 

 the general appearance of King's S. Goldfussiy Mon. pi. 12, 

 figs. 1—11, that I cannot doubt its identity with 0. excavatus. 



The princijial character by which Geinitz w^ould separate his 

 0. excavatus from 0. Goldfussi is the sinus of the ventral valve. 

 This is not a constant character, and certainly not a specific one. 

 Mr. King observes (Mon. j). 99) — " The arrangement of the 

 spines constitutes a capital distinctive character for this species ;" 

 and, strangely enough, he refers to a shell doubtfully referred to 

 Goldfussi by Geinitz and excluded from it by King, as a proof. 

 Now, this excluded shell with the " capital distinctive characters" 

 is nothing more than Mr. King's S. Goldfussi, for it is the 

 0. excavatus, Gein. After all the difficulties attending the study 

 of this species, one turns with pleasure to Mr. Davidson's excel- 

 lent plate iii., and to the original diagnosis of this shell by Mr. 

 N. Winch, in the " Gcol. Trans." vol. iv. p. 10, " A species of 

 Donax with hair-like spines." 



The regular form of. this shell, " Mon., Brit. Perm. Brach." 

 pi. 3, figs. 19, 20, 21, 22, ought to be considered ^s the typical 

 S. Goldfussi; and if it be thought desirable to distinguish the 

 other by a varietal name, excavata can be a]:)plicd to it. But 



