64 Prof. T. R. Jones on the 



Nat. Hist., October 1890, p. 323, pi. xi. % Gh). Possibly 

 this species {ibid. figs. 5-8) should be separated from Entomis. 

 Fig. 8 a has a resemblance to the form distinguished by E. O. 

 Ulrich as Barychilina (Journ. Cincinn. Soc. N. H. vol. xiii. 

 1891, p. 199, pi. xiii. figs. 1-4), which has longitudinal and 

 sinuous strife, with pitted interstices, unequal and thick 

 valves, without a mid-dorsal furrow^ though Ulrich's fig. 2 a 

 seems to have a trace of it. E. variostriata in its younger 

 stages has the definite Entomidian sulcus, and, as other 

 species of this genus occasionally exchange the furrow for a 

 ])it, it would not be necessary to make a separate genus on 

 that ground. The different style of ornament, however — 

 prickly ridges in one and meshed interstices in the other — 

 may be a reason, as well as the coarser growth of the valves. 



6ome of the Devonian Eatomides 2i]-)]^Q2tx to have had simple 

 and smooth stride (for instance, figs. 9 and 18, pi. xi., Ann. & 

 Mag. Nat. Hist. ser. 5, vol. iv. 1879) ; but E. serratostriata 

 had prickles along its costulte or raised strias (see page 321, 

 Ann. & Mag. Nat. Hist. ser. 6, vol. vi. 1890), indications of 

 which are little pits in the hollow casts or impressions 

 (intaglio) of the valves, and not filling the breadth of tlie 

 interspaces. E. variostriata, on the contrary, shows a square 

 mesh work (fig. 6 Z>, pi. xi., op. cit.), of relatively large 

 pattern, filling the space between the strife. 



Among the more or less modified specimens of E. serrato- 

 striata (Ann. & Mag. Nat. Hist. ser. 5, vol. iv. 1879, p. 101, 

 pi. xi.) fig. 9 shows the pit only ; in figs. 2 and 14 a faint 

 trace of the sulcus accompanies the central spot ; and in fig. 9 

 both are absent. The collocation, however, and general 

 mutual resemblance of the numerous specimens support the 

 idea that they are congeneric and specifically the same. 



In well-preserved specimens E. tmriostriata, Clarke {ibid. 

 vol. vi. 1890, p. 323, pi. xi. fig. 8 a), has the pit instead of 

 the sulcus, whilst figs. 5-7 show the sulcus only. So also 

 in Primitia we may have — (1) the furrow, (2) furrow and pit, 

 (3) pit only. 



On account of the difi^erent style of ornament and the 

 coarser growth of the valves there is reason for making the 

 separate genus (^Barychilina) ; and, even if it has no sulcus 

 at right angles with the hinge-line, but only a central pit, we 

 find that some allied genera have similar modifications, 



Baryckilina semen is from the Devonian Limestone with 

 Clymenia annulata^ Miiuster, at Hadiberg, near Briiunj 

 Moravia. 



