398 Prof. T. E. Jones on the 



circular, ridge-like border, interrupted on two sides by the 

 line and the sulcus, the ends of which in the depression are 

 separated one from the other by a central tubercle. More- 

 over there are numerous very delicate, wavy, radiating, vas- 

 cular impressions, starting from the pit, crossing its bounding 

 ridge, and meandering over the outside of the cast. Size : 

 length Y2, breadth tVj height yV "^ch. 



III. Comparison of the three Specimens (I., II. 1, TI. 2). — 

 They agree in their more or less hemispherical shape, 

 although pressure may have modified eacli. It is quite pos- 

 sible that the specimen " I." (fig. 12) has suffered lateral 

 pressure so much as to change the longer to the shorter axis ; 

 for the analogous furrow in Entomis &c. is transverse to, and 

 not parallel with, the long axis, unless under pressure acting 

 on the ends. In this specimen there are neither vascular 

 markings nor marginal rim preserved, which features indicate 

 alliance to Leperditia^ Eyitomis^ &c. 



Specimen " II. 1 " (fig. 13) shows signs of having been 

 slightly crushed ; its shape therefore is not strictly typical, 

 and the umbilicus may have been obliterated in the conical 

 apex. The smooth marginal rim, which is seen also in Leper- 

 ditia, though not so continuous as here, indicates that this 

 was one of two valves, as in Leperditia &c. ; but the extreme 

 convexity of each valve (if equal, or nearly so) would make 

 an unusually globular bivalve Entomostracan. Entomocon- 

 chus glolulosus has nearly similar proportions ; but it is more 

 uniformly convex and has other distinctive peculiarities. 



Specimen " II. 2 " (fig. 11) seems to me to be the best 

 preserved of the three known examples of this obscure organ- 

 ism. The hemispherical shape of the valve appears to have 

 been undisturbed, and the form of its dorsal and ventral 

 margins, with the flanged rim, to have escaped modification. 

 The central and, as it were, umbilical depression, with its 

 central tubercle, surrounding ridge, and vascular impressions, 

 retain their shape; and the "nuchal" furrow, marking the 

 dorsal region, is distinct. The thin line across the ventral 

 region, and continuous with the sulcus, looks natural, and may 

 be analogous to the perfectly transverse sulcus in Entomidella. 



Entomis tnherosa is represented by some imperfect castSj 

 and E, Hasioelliana by others, in the same mudstone of the 

 Pentland Hills that yielded Mr. Haswell's specimens (II. 1 

 and 2) ; and in some of them vascular radiation clearly 

 accompanies the extremity of the dorsal " nuchal " furrow 

 where it curves round a small central tubercle. Here is a 

 close family resemblance ; but E. tuberosa and E. Haswel- 

 liana are nevertheless Leperditioid in shape, the furrow is 



