Dr. Ivor Thomas — Devonian Fossils from Cormoall. 99 



Langenaubach near Haiger, Germany, Kielce in Poland, Rostellec 

 near Brest, Cabrieres in south of France, and apparently also in the 

 Ural District (10, pp. 155, 156 ; 16«, p. 184). Dr. 11. Wedekind has 

 recently discussed and subdivided this horizon in an interesting 

 contribution entitled "Die Cephalopodenfauna des hoheren Ober- 

 devon am Enkeberge " (17, pp. 565-634). 



Remarks. — The employment of the name Trimerocephalus in the 

 above description is in accordance with the usual interpretation. 

 Professor Giirich would base the distinction between the typical 

 Phacops and Trimerocephalus on the size of the angle made by the 

 dorsal furrows bounding the glabella, which- in the case of 

 Trimerocephalus would be about 50° and Phacops 80°-90° (9, p. 362). 

 I agree with Mr. Cowper Eeed that this distinction is quite insufficient 

 (15, p. 226). The subgenus was originally founded by M'Coy (12, 

 p. 404) upon Trinucleus "bleeds, Miinst. (13, p. 116, pi. x, fig. 6), 

 a form in which he considered the eyes to be absent. Giimbel 

 (8, pi. A, figs. 7-9) refigured Miinster's original, and identified it with 

 Phacops cryptophthalmus, Emmrich (2, pp. 27, 61). Miinster's figure 

 is too poor to be of use, while Emmriclrs rather scanty description is 

 unaccompanied by illustrations. 



The poor state of preservation of thorax and pygidium prevents 

 as clear a discrimination of certain parts of our species as could be 

 desired. In the general shape of the head-shield it resembles Phacops 

 c^cus^ Giirich (9, pp. 362, 363, pi. xv, fig. 4), from the middle part of 

 the Upper Devonian of the north-east border of Kadzielnia, Poland, 

 a form which has also been described by Dr. Drevermann from the 

 Clymenien-Kalk of Langenaubach {\c, pp. 114, 115, pi. xiii, fig. 4). 

 Phacops ccecus differs, however, among other respects, in the absence 

 of eyes, in the presence of a broader border and a broader occijiital 

 ring, in the possession of more extended postero-lateral margins of the 

 head-shield, a greater angle between the dorsal furrows bounding the 

 glabella, and a less tumid frontal margin of the glabella. 



Phacops {^Trimerocephalus'i') lotzi, Drevermann {\c, pp. 117, 118, 

 pi. xiii, fig. 7), also bears a superficial resemblance to the form 

 described. The eye in Dr. Drevermann's species differs in the 

 possession of eight facets arranged in two rows, while the marginal 

 border is broader, the postero-lateral margin of the head-shield more 

 extended posteriorly, the frontal margin of the glabella more angular, 

 and the angle of the dorsal furrows bounding the glabella smaller. 



The Portquin species differs from Giimbel's figure of Phacops 

 cryptophthalmus, Emmrich ( = T. '? Icevis of Miinster), in the relative pro- 

 portions of the length and breadth of the head-shield, in the narrower 

 occipital ring and marginal border, and the different arrangement and 

 smaller number of eye facets. 



In describing Phacops {^Trimerocephalus^ Icevis (Miinst.), as a synonym 

 with which both he, M'Coy, and Giimbel place Calymene Icevis of Phillips 

 (14, pp. 129, 130, pi. Iv, fig. 250), Salter states that the "eyes are 

 absent in oiir English specimens but probably present in perfect 

 individuals " (16, p. 17). It is possible that in many cases the apparent 

 absence of eyes is accounted for by the poor state of preservation. 



Phillips has recorded Phacops {Trimerocephahis) /t?v/« (Miinst.) under 



