106 Henry Woodward — On British Fossil Arthropoda. 



The bed lies rather high in the " middle Coal series." 



The specimens figured in the accompanying Woodcut, Figs. 1 and 

 2, are considered by Mr. Salter to be the lateral portions of the 

 head-shield, which he thinks must have been at least 8 or 9 inches 

 across. It shows a strongly arched border running out into a short 

 acuminate broad spine, into which a strongly curved sharpish ridge 

 runs from about the upper central portion. The space outside and 

 above the ridge is flat, and is oruamented with small rounded 

 tubercles scattered irregularly over its surface ; below the ridge 

 there are fewer tubercles, but near the hinder border there are two 

 (and part of a third) large mammillated tubercular spines ranged 

 about equidistant from one another ; they are directed backwards, 

 and are fully a third of an inch in length, and as much in diameter 

 at the swollen base. 



Another fragment (Woodcut, Fig. 3), also referred by Mr. Salter 

 to the head, shows large and small tubercles upon its surface. 



Mr. Salter speaks of " at least six, and probably more, of the large 

 mammillated tubercular spines along the hinder border " (of Figs. 1 

 and 2). The explanation of this is to be found by referring to the 

 accompanying woodcut illustrating Mr. Salter's paper, which by 

 the kindness of the Council of the Ceological Society we are able 

 to reproduce here (see Quart. Journ. Geol. Soc, vol. xix., p. 85) 

 when it will be seen that this specimen (Fig. 2) has been drawn 

 twice over (once reversed, and once in its natural position), so as to 

 give the effect of a crescent-shaped shield. But only the piece 

 represented as Fig. 2^ exists, and after careful comparison I am 

 quite unable to refer it to the head-shield of any known Crustacean. 



Eeferring to the above woodcut, Mr. Salter observes, " Although I 

 have supposed Figs. 1 and 2 to belong to the head, I have really little 

 else to recommend this view than the great comparative size and 

 breadth, and the general form, which is like that of the hinder angles 

 of the head of the Scotch Eurypterus." ^ 



Mr. Salter then proceeds to contrast his Eurypterus mammatus with 

 the Arthropleura armata of Jordan, a species founded upon the 

 fragments of a large Crustacean (?) from the Coal-measures of 

 Saarbruck, Ehenish Prussia. 



If the subjoined woodcut (Fig. 9, B) of Arthropleura armata be 

 compared with Woodcut Fig. 1, a somewhat similar piece (marked p), 

 having a corresponding raised border and similar arrangement of 

 tubercles, will be seen, suggesting that this pointed portion (Fig. 1) 

 may more likely be the pleuron of a trilobed segment. This inter- 

 pretation, although rejected by Mr. Salter, seems to me, on many 



1 It is quite apparent, however, from Mr. Salter's description, that he was under 

 the impression that tivo specimens existed m reality as well as in his figure. I have 

 therefore specially noticed this, lest hereafter it should be supposed that one of these 

 curious fragments had really been lost. 



2 If by the Scotch Eurypterus Mr. Salter refers to E. Scouleri, a comparison 

 between the fragment of E. mammatus and the entire head of E. Scouleri will satisfy 

 any palaeontologist that such a hinder angle could not possibly be fitted to the carapace 

 of the latter ; the curvature and ornamentation being both incongruous. No other 

 form with which we are acquainted could have required so large an epimeral piece 

 save the great Devonian Stylonurus Scoticus. 



