BRITISH FOSSILS. 



3 



an uncompressed specimen, but they are mostly distorted, and, as 

 noticed by Mr. Pengelly, the head is generally disjointed from the 

 body and inverted, as if the animal had habitually kept it bent under, 

 and been preserved in the slate in that position. In that posture, 

 and exposed to the accidents of slaty cleavage, it is often difficult 

 to distinguish the parts correctly ; and the juxtaposition of two 

 specimens, or the extra elongation along the line of cleavage, have 

 often given rise to a specimen with apparently more than the proper 

 number of body rings, and to all sorts of abnormal proportions of 

 the various parts. 



Locality and Geological Position. — Upper Devonian. Knowl 

 Hill, Newton Bushell. It is quoted by Phillips from S. Devon, at 

 Mudstone and Durlstone Bay. I think there is much doubt of these 

 Lower DcvonianloGdliiiQ^, but less doubt about Brushford, N. Devon, 

 in the Marwood or Pilton group. 



Explanation of Plate IX. 



Fig. 1. Phacops {Trimerocephahs) lavis, Miinster. Specimens from Knowl Hill, 



Newton Bushell. (Mr. Pengelly's cabinet.) 

 Figs. 2, 3. From the same locality and cabinet. Specimens in which the head has 



been disjointed from the body and reversed in position. (See also fig. 5.) 

 Fig. 4. Thoracic ring and tail from Mr. Vicary's cabinet. 



Fig. 5. Original specimen figured by Sowerby in the Geol. Trans., 2nd series, vol. v. 

 (Same locality.) 



Fig. 6. Phacops (Triineroc. ?) cryptophthalmus, l&mmr., from Nassau. Copy of Sand- 

 berger's figure to show the differences of the species. P. cryptophthahnus 

 is often confounded with P. Icevis, 



