2 DEVONIAN FAUNA. 



the genera Bactropus and Tropidocaris (?) ; and Ostracods of the genera Entomis, 

 Cyprosina, Polycope, Cypridina (?), Cypridella, and Cypridinella (?), of which the 

 Cyprosina is at once the largest and the most abundant. Lummaton seems to be 

 far more prolific in Crustacea than Wolborough; but this may have been due 

 to the greater preserving power of its sediment, that of Wolborough having been 

 unsuitable to retain such delicate organisms as Trilobites in a sufficiently perfect 

 state to attract the collector's eye. Neither has this latter place been specially 

 searched for Ostracods, and such small fossils would almost certainly escape notice 

 unless attention were especially turned to them. Finally, most of the Crustacea 

 at Lummaton have occurred in the bed at the top of the quarry, which is 

 apparently little else than a shell-heap, and which was probably a local and 

 littoral deposit. This would explain the fact that the Trilobites are almost always 

 found there in a fragmentary condition ; for most likely they had decayed and 

 fallen asunder before they reached the place of deposition. 



Order— TRILOB1TA. 



I. Family. — Pbacopim;, Salter, 1864. 



1. Genus. — Phacops, 1 Emmerich, 1839. 



The Trilobites now included in this genus were formerly classed with Calymene. 

 It is defined by the shape of the facial suture, the large and conical faceted eye, 

 the eleven segments of the thorax with grooved pleuraB, and the large glabella 

 broadest in front. Ph. latifrons, Bronn, is the typical species. The restricted 

 genus extends from the Upper Silurian to the Upper Devonian, but the neighbouring 

 genera, which have been usually regarded as sub-genera of Phacops, begin at the 

 base of the Lower Silurian. 



1. Phacops bateacheus, Whidborne. PI. I, figs. 2 — 7. 



P1841. Calymene gbantjlata, Phil. Pal. Foss., p. 128, pi. lvi, figs. 248 g, h, i, 



only. 

 1864. Phacops gbanulattjs, Salt. Mon. Brit. Tril., p. 18, pi. i, fig. 1, only. 

 1889. — batbacheus, Whidb. G-eol. Mag., dec. 3, vol. vi, p. 28. 



Description. — Head wide, convex, flattened above. Glabella pentangular, 

 roughly equilateral, bluntly pointed in front, slightly convex above, curving 



1 Though &\p is feminine, its derivative Cyclops is masculine. G-oldfuss having used the names 

 of Brontes and Arges (two Cyclopes), Emmerich seems to have referred to this in the word Phacops. 

 It would therefore be masculiue. 



