272 (9m the Palceozoic Bivalved Entomostraca. 



ences are perceptible in outline and contour. This species, 

 however, with other smooth and still more Leperditioid forms, 

 has been lately referred bj me to a separate group, with the 

 generic name Aparchites (Ann. & Mag. Nat. Hist. May 1889, 

 pp. 384, 385), and this appears to be the best group to which to 

 refer the specimens (from Wisby) here noticed, although such 

 non-sulcate Primitian forms are rarely so very symmetrical 

 as these. 



1. Aparchites decoratiis, sp. nov. 

 (PI. XV. figs. 12 a, b, c.) 



Proportions*:— L. 18. H. 15. Th. 91 



Carapace lenticular, almost circular in side view, with the 

 dorsal margin partly straight ; equally convex on the sides, 

 as shown by the elliptical outline in fig. 12 ^, but rather 

 fuller towards the dorsal than towards the ventral border 

 (fig. 12c). Surface of valves minutely punctate except along 

 a narrow area all round. 



2. Aparchites siviplex^ sp. nov. 

 (PI. XV. figs. 13 a, h, c.) 



Proportions :— L. 18. H. 14. Th. 9i. 



This smooth, convex, lenticular carapace much resembles 

 Ap. decoratus, but it is rather more ovate, one end (anterior) 

 being somewhat elliptically curved and with less boldness 

 than in fig. 12 a; the hinge-line takes up a greater portion 

 of the dorsal margin, giving a definite local straightness, and 

 the surface has no ornament. In these features there is some 

 approach to Aparchites ohsoletus, J. & H. (Ann. & Mag. Nat. 

 Hist. December 1865, pi. xiii. fig. 12). 



3. Aparchites Lindstrmmii^ sp. nov. 

 (PI. XV. figs. 14 a, h.) 



Proportions :— L. 13. H. 10. Th. 4^. 



This is rather more Leperditioid than either of the two 

 described above, and, excepting that the ends of its dorsal 

 margin are not sharp and that it is less convex and very much 

 smaller, it much resembles A. Whiteavesii^ Jones (Ann. & 

 Mag. Nat. Hist. May 1889, pp. 384, 385, pi. xvii. fig. 10). 



* For figures 12, 13, 14, the proportions are taken on the same scale as 

 for figs. 1-11. 



