30 Dr. H. Woochvard — Devonian Trilobites from Cornwall. 



The Devonian species of ITomalonotus occur in Cornwall and 

 Devon, and extend into Germany and Spain. One species is met 

 with as far off as South Africa (IT. Hersclieli). 



All the Devonian Trilobites appear to be referable to Mr. Salter's 

 section of Horaalonoti with spines, which he named Burmeisteria : 

 this division includes all those species having the body elongate, 

 convex ; head triangular ; eyes approximate on gibbous cheeks ; 

 glabella distinct, lobeless, sinuous ; thorax slightly lobed and 

 spinous, as is also the many-ribbed, pointed tail. He takes for 

 his type M. Serscheli, from the Devonian. 



Mr. Salter's Somalonotus elongatus is founded upon a tail only, 

 remarkable, even in this elongated genus, for its length and shape. 

 This form is very strongly trilobed, and appears to have had four 

 pairs of spines along its median axis and two pairs upon the 

 lateral portion. (See Salter : Mon. Pal. Soc, 1865, pt. ii, p. 122, 

 pi. X, figs. 1, 2.) 



Homalonotus Champernownei has little or no signs of trilobation, 

 and is rather larger than the celebrated H. delpTiinocephalus from 

 the Wenlock Limestone of Dudley ; it has thirteen free moveable 

 thoracic segments with broadly expanded pleurae, each rib armed 

 with a pair of spines placed about one inch apart; the head also 

 had three pairs of spines placed on the lateral portion, and three 

 along the medial line ; there is no evidence of cheek-spines ; the 

 pygidium is imperfect. (See Geol. Mag., 1881, Dec. II, Vol. VIII, 

 p. 489, PI. XIII.) 



In Mr. Barratt's specimen from a cove in the Devonian slates 

 of Trevose Head, Cornwall, we have only evidence of one side of 

 the pygidium, five of the posterior free thoracic segments, and 

 fragments of others. Assuming these to have been compressed 

 longitudinally so as to make them appear disproportionately broad 

 and short, they still have the characteristic deep falcate margins to 

 the free segments and the six or seven well-marked coalesced 

 segments to the pygidium seen in other species of this genus ; but, 

 though only a fragment, we notice that each segment, both in the 

 free thoracic rings and in the coalesced segments of the tail, is 

 marked by a single row of small rounded tubercles uniform in size, 

 ten on each pleura and an uncertain number on the axis of the 

 body ; those on the coalesced segments of the tail diminishing in 

 number backwards from ten to eight, to six, to four, to three. The 

 ribs of the tail do not extend to the margin, but leave a smooth 

 rounded border. It would be impossible to give a more detailed 

 description of so mere a fragment, but the single row of extremely 

 regular tubercles on each segment suffices to separate it from other 

 Devonian or Silurian forms with which I am acquainted. The 

 Figure, which is reduced to two-thirds natural size, serves to convey 

 a correct idea of this interesting fragment. 



So soon as attention is directed to the occurrence of Trilobites 

 in these Devonian slates at Trevose, no doubt many more specimens 

 will be found to reward the diligent seeker after organic remains. 

 Dr. Arthur Smith Woodward, F.K.S., in his Catalogue of Fossil 



