Woodward and Ethendge — On Dlthyrocaris. 483 



in. size, is one-tliird less than Dr. Scouler's original specimen of 

 D. testudinea (Figure 1 in our Plate), obtained by him "about a 

 mile to the east of Paisley" (op. cit. p. 136). The same raised 

 oblique re-curved and divaricating lines observable in the original 

 specimen of D. testudinea mark this smaller example from East 

 Kilbride ; a lateral median ridge (seen on each side in Dr. Scouler's 

 specimen) marks the centre intermediate between the margin and 

 the dorsal line of the carapace. 



The lateral margin of the carapace along, its posterior half is 

 relieved by more finely and closely arranged strige than those which 

 mark the remainder of the shield. 



Dimensions of Scouler's original specimen of D. testudinea (figured 

 in our Plate XVI. Fig. 1): greatest length of carapace, from latero- 

 posterior spine to frontal border, 35 millimetres ; length of dorsal 

 line, 30 mm. ; greatest breadth of carapace, 30 mm. ; length of caudal 

 segments, including caudal spine, 25 mm.; 3 caudal spines, each' 

 15 mm. long. 



Dimensions of Survey specimen of D. testudinea :. greatest length, 

 22 mm. ; greatest breadth of the half shield, 8 mm^. 



Localities. — Old quarry on- North Lickprivick Farm, East Kilbride, 

 in shale above the Maiai Limestone ; Jock's burn, above Hallcraig 

 Bridge, about one mile west of Carluke, in the "Lingul a Limestone"; 

 Kirktonholm Cement Works, and the Glebe Quarrj^ East Kilbride, 

 in shale above the Calderwood Cement Stone. All members of 

 the Lower Carboniferous Limestone Group. — Collected by Messrs. 

 Bennie and Paton. 



2. BirnTRocARis tricornis, Scouler (Plate XVI. Fig, 2, Scouler's 

 original specimen; Fig. 3, Survey specimen). 



The impression and counterpart of the very beautiful specimen 

 (Plate XVI. Fig. 3) which we have referred to this species was 

 obtained by Mr. J, Bennie from the shale above the Calderwood 

 Cement-stone, Carboniferous Limestone series. East Kilbi'ide. 



It is of the utmost importance, as it affords us an entirely new 

 interpretation of Scouler's D. trieornis (Plate XVI. Fig. 2), as well 

 as the means of fully describing its characters, which, from the 

 decorticated condition of the original specimen, was hardly possible. 



General Portlock, in his grand work, " Geological Eepoi^ on 

 Londonderry," etc., 1843, acutely observes (p. 313) concerning 

 Argas (Dithyrocaris) trieornis, that "in all probability it depends 

 on an illusive appearance produced by the overlapping of the crusts 

 of difi'erent individuals." This, however, is not the true explanation 

 of its anomalous specific character. The three spines truly belong 

 to the carajoace, but the so-called "anterior border" of Scouler 

 (Fig. 2 p) is really the posterior margin, the abdominal seg- 

 ments and tail-spines (c) having become displaced during the 

 decomposition of the softer parts of the animal, so as to protrude 

 from the anterior extremity of the carapace. This is a common 

 occurrence with the specimens of Ceratiocaris papilio from the 

 U. Silui'ian of Lesmahagow, Lanarkshire (as shown by H. Wood- 



