40 Messrs. Jones and Kirkby on Carboniferous Entomostraca^ 



forms described in our former memoir, it will be convenient to 

 retain the name as that of a variety. 



In the second part of his ' Verstein. Grauwacken Sachsens ' 

 (1853), p. 23, Dr. Geinitz described a small Bivalve Entomostra- 

 can, which he termed " Cytherina subrecta, Portlock,^^ and which 

 he found at the Gunzenberg, near Plauen, in company with the 

 tail-spines of Dithyrocaris Murchisoni ; and he remarked that, 

 as Portlock found his specimens with Dithyrocaris, the circum- 

 stances are alike for the Silurian and the Carboniferous organ- 

 isms. But Geinitz^s Cytherina subrecta, as illustrated by him at 

 pi. 19. fig. 20 of the work above referred to, is very different 

 in appearance from Portlock's C. subrecta, being narrower in 

 proportion, incurved both on the dorsal and ventral margins, 

 bordered by a flat rim (apparently) all round, and rounded 

 equally at the ends. The Silurian spines of the so-called 

 " Dithyrocaris " are very probably those of Ceratiocaris. 



Leperditia Okeni of the size and form of L. subrecta occurs 

 at Fermanagh, Ireland (Portlock) ; Blackwell, near Bristol 

 (Moore) ; Great Orme's Head (Dr. Holl) ; Whorlton, Teesdale 

 (Parker) ; Wyebourne, Cumberland (Bland) ; banks of the 

 Wansbeek (Pecket) ; Barnard Castle (Barron) ; Carluke (Hunter); 

 West Broadstone, Ayrshire (Thomson) ; Orchard, near Thorn- 

 liebank (Armstrong) ; Gare, Carluke (Thomson) ; Howrat 

 Quarry, near Dairy (Armstrong) ; Craigenglen (Young and 

 Crosskey) ; Campbeltown (Thomson) ; Carboniferous Limestone, 

 Ashford, Derbyshire (Geol. Survey); Carboniferous Shales, 

 half a mile south of Mitcheldean (Geol. Survey) ; and at many 

 places in Ireland (Griffith and Geological Surveyors) . See further 

 on. 



1844. M'Coy. — In 1844 Professor M'Coy considerably en- 

 larged our knowledge of the Entomostraca of the Carboniferous 

 Rocks by the description and illustration of twenty-two forms 

 (including Entomoconchus Scouleri), besides two species of 

 Dithyrocaris {D. Scouleri and D. tenuistriatus), all from the 

 Lower Carboniferous strata of Ireland. 



Thanks to the courtesy of Sir Richard Griffith, Bart., we have 

 been enabled to examine many of the specimens described by 

 Prof. M'Coy, and thereby to make our comparisons more surely. 



The localities of nearly all the specimens described by M'Coy 

 (and all that we have had in hand) have been given by Sir R. 

 Griffith in the ' Journal Geol. Soc. Dublin,' vol. ix. (1860), pp. 

 21 &c. ; and indeed the specimens retain their original labels, 

 with the localities indicated. 



On comparing the specimens with the figures in the ' Synopsis 

 of the Characters of the Mountain-Limestone Fossils of Ireland,' 

 pi. 23. figs. 4-25, we fail in recognizing several of M'Coy's 



