DITHYROCARIS SCOULERL 157 



111 his ' Systematic Description of the British PaU^ozoic Fossils in the Geolo- 

 gical Museum of the University of Cambridge,' 1851, Fasciculus I, pp. 81, 82, 

 after mentioning " Difhi/rocaris, Scouler, MS.," as one of the Apodiadas, M'Coy 

 gave a generic description of it, from his knowledge evidently of I). CoJei and 

 D. Scouleri, thus : 



" Ge7t. Char. — Carajmce semi-oval, the two sides meeting along the middle at a very obtuse 

 angle ; anterior end rounded, often with an obscure notch in front ; posterior end subtruucate, with 

 the lateral angles produced backwards into short, flat, angular spines ; surface faintly marked with 

 irregular imbricating striae, the margins being usually thickened and corrugated, and with three well- 

 marked longitudinal ridges, one in the middle extending the eutire length, and one on each side not 

 reaching the front margin ; within and anterior to the ends of these latter are two small, obliquely 

 longitudinal, sigmoid ridges, extending inwards and forwards towards the mesial ridge ; posterior 

 part of the body naked, tail terminating in three long, strong, equal, triangular spines, the middle 

 one bayonet-shaped with a triangubir section, the lateral ones flattened. I have not yet detected any 

 trace of eyes in this genus, which seems closely allied to Apus." 



He then passingly alluded to D. Scouleri, M'Coy, but added no particulars. 

 Our friends at Dublin and elsewhere have not been able to find the orio-inal 

 specimen figured and described by Sir Frederick M'Coy. 



In response to our inquiry respecting the original specimen, the trustees of 

 the Griffith Collection have obligingly sent to us, as the only evidence they can 

 find of M'Coy's D. Scouleri. in that Collection, a plaster cast and a photograph of 

 the slab labelled as representing that species, from Aughnaclogh. It shows 

 only a feeble outline of what may be a Di.thyrocaris ; and we have given a repre- 

 sentation of it in PI. XXV, fig. 7. The outline seems to represent an imperfect 

 suboblong carapace; one moiety is about 32 mm. long and 13 mm. wide. As far 

 as recognisable this may have belonged to a small D. Colei, such as PI. XXII, 

 fig. 7, and PL XXVII, fig. 5. 



By some writers on Bifhi/rocaris, D. Scouleri, M'Coy, has been referred to 

 D testudinea of Scouler,' to which the pubhshed figure bears some resemblance 

 in general appearance. The peculiar linear ornamentation of the valves or lateral 

 moieties, however, is altogether wanting in M'Coy's elaborate description, and in 

 the figure which he gave of the species, reproduced here in PL XXV, figs. 6 a, b, c. 

 The obliquely marked abdominal plate in fig. 6 a is doubtful in character. 



Sir Richard Griffith, in the 'Journ. Geol. Soc. Dublin,' vol. ix, 1862, p. 48, 

 refers D. Scouleri to the Carboniferous Slate, or Lower Limestone Shale, of the 

 Yellow Sandstone Group (at page 100 — the Arenaceous Shale of that group), at 

 Aughnaclogh, Clogher, co. Tyrone. 



1 Seb p. 485, foot-note, ' Geol. Mag.,' vol. x, 1873 ; and dec. 2, vol. i, 1874, p. 109. 



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