K5 TRIMEROCEPHALUS. 



Subgenus — Trimerocephaltjs, as above. 

 1. Piiacops (Trimerocephaltjs) l^tvis, Miinst., sp. PI. I, figs. 5, 6, 7. 



Asaphus or Trinucleus, Sow. Geol. Trans., 2nd series, vol. v, pi. 57, fig. 30, 1840. 

 Trinucleus l^vis, Munster. Beitrage, Heft 5, t. x, fig. 6, 1842. 

 Calymene LiEVis, Phillips. Palaeozoic Fossils, pi. 55, fig. 250 (1841). 

 Trimerocephalus LiEVis, M'Coy. Ann. Nat. Hist., vol. iv, p. 404, woodcut, 1849. 

 — — Hid. Synopsis Woodw. Mus., 1851, p. 178. 



Diagnosis. — P. [Trim.) late ovatus, lavis, glabella latissimd, brevi, genas subspharicas 

 trigonas impendente, lobis basalibus minutis distinctis. Axis thoracis angustus, fulcro 

 pleurarum axin approximate, sulcoque brevi. Cauda latissima brevis, axi longo h-annulato, 

 lateribus 4-stileosis, margine nullo. 



This was first figured in England from very imperfect specimens, which came from 

 the only English locality yet known, viz., the Knowl Hill, near Newton Bushel. They 

 are mostly distorted, and, as first -noticed by Mr. Pengelly, the head is usually disjoined 

 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 condition it is often difficult to dis- 

 tinguish the parts correctly. 



But the number of specimens already collected enable us to restore the animal pretty 

 completely ; and there is not much doubt that it is identified rightly with the Trinucleus 

 lavis of Minister. 1 Both Mr. Sowerby and Professor M'Coy have recognized it for this 

 fossil, and Dr. Sandberger has quoted it as a synonym, only he mixes up two or three 

 other species with it, — among others the {Calymene) Phacops lavis of Munster. 



It is clear, however, that it is distinct from the small trilobite originally named Calymene 

 lavis by Munster, and next described ; as the following description will show. 



And should it prove that the fossil called Cal. lavis by Munster is a real species, we 

 should have to find a new name for this. Dr. Sandberger wishes to connect it with the 

 Phacops cryptophthalmus of Emmerich, a fossil also occurring in the same Devonian 

 formation. But though much disposed to believe that our fossil has true but superficial 

 eyes, which are not easily preserved, I cannot think that this is a true identification. The 

 eye of P. cryptophthalmus is very much more distinct, and I have figured what I believe 

 to be that species, with the eye, a little further on. P. cryptophthalmus, too, is described 

 and figured by Dr. Sandberger as having a larger semicircular tail, while ours has a very 

 short one. I may now describe the Knowl Hill fossil. 



1 From the red sliales of Guttendorf. The head only is figured by Miinster. 



