Professor T. R. Jones — On a Malayan Esther iella. 51 



more distinct ou the anterior than on the posterior moiety of the 

 valve, and sometimes more so on either than in the middle. In 

 some valves, however, the radial lines are persistent throughout the 

 ventral region, as, for instance, in the specimens shown by Figs. 2-4. 

 A noticeable feature due to existence of these very thin radial sulci 

 is that the surface of the adult shell has the aspect of having been 

 squeezed transversely, and thus modified by the intervals between 

 these slight (but sufficiently deep) furrows being puckered up into 

 small, regular, parallel, radial ridges, crossed by the frequent 

 successional edges of growth in the shell, and by the interstices of 

 the concentric costse. (See Fig. 4.) 



Very fine delicate parallel lines are also recognizable on the radial 

 ridges (see Fig. 4). The radial lines and ridges supply the generic 

 characters o{ Esther iella, Yfexs^ (Zeitsch. deutsch.Geol. Ges., vol. xxvi, 

 1875, p. 711, note ; and E. Jones, Geol. Mag., 1891, p. 53). 



Comparison of the Malayan with some Sicilian Species. 



Some closely allied fossil species (presumably of Triassic age) 

 have been figured as Estlierice by Professors G. G. Gemmellaro ^ and 

 E. Salinas,^ to which these Malayan specimens have much resem- 

 blance. Professor Salinas gives full descriptions of the species he 

 has figured. 



Comparing the best of our specimens (PI. 11, Figs. 1-3) with 

 Salinas' Estheria radiata, op. cit., pl. i, fig. 6, we see that they are 

 rather larger, that the dorsal border is more strongly modified by 

 the umbo, and has its two moieties more unequal than in Salinas' 

 fig. 6 ; but it is nearly straight throughout, although slightly 

 modified by the somewhat protruding umbo. Specimens ' A ' and 

 ' B ' differ from Estheria Giofaloi, Salinas, op. cit., pl. i, figs. 1-5 

 (especially figs, 1-3), in its shorter dorsal edge and less oblong 

 outline. The subtrigonal aspect of figs. 2 and 3 may be due to 

 a partial imbedment, such as occurs with numerous shells of 

 a similar shape. 



In the Malayan specimens we also find that the concentrics are 

 broader, each bearing five or six costulee ; and that the radials are 

 more numerous, thicker, and stronger ; also that the Sicilian figures 

 do not show any small intercalated concentrics, either on the broad 

 ribs or in the interspaces. 



Some of the above-mentioned differences in form are not of much 

 importance ; but on account of the numerous, thin, intercalated 

 concentrics, and the radial lines occurring all over the ventral region 

 (Pl. II, Figs. 1-4), I prefer to regard this form as somewhat 

 different from Salinas' Estheria radiata, and to name it Estheriella 

 radiata (Salinas), var. multilineata, nov. 



An analogous structural aspect of the surface in a valve is shown 

 by figs. 5-Q (particularly fig. 66) in plate v of vol. ix of the Trans. 



1 G. G. Gemmellaro, " Sul Trias della regione occidentale della Sicilia " : Atti 

 Accad. Lincei, ser. iii, vol. xii (1882), Rome (Memorie), pp. 451-473 ; pp. 455-456, 

 Estheria Giofaloi, Gemm. (not described), pl. v, fig. 13. 



2 Emmanuele Salinas: " Sulle Esterie del Trias di Sicilia," small 4to, Palermo 

 .(Museo Geol. Min, E. Univ. Palermo), 1897, pp. 1-12, pi. i. 



