138 H. HICKS ON THE EOSSILIFEROTJS 



A very short diagnosis of the two new species may be added, 

 leaving the fuller descriptions until better specimens have been 

 found. 



Caryocaeis Mareii, n. sp. 



Carapace about f inch long, more pointed than rounded ante- 

 riorly, subtruncate posteriorly ; width at the broadest part about J 

 inch. Shell thick and horny-looking, probably similar in composition 

 to the shell of a Trilobite. The surface is convex over about three 

 quarters of its length, and is marked with at least three moderately 

 deep furrows, bent considerably forwards, and which seem to divide 

 it into lobes. The carapace has the appearance of being much 

 narrower than in C. Wrightii. 



^Eglina Hughesii, n. sp. 



xipparently not more than h inch in length, sometimes much 

 less. Head smooth, inflated, and convex, longer and wider than 

 the tail. Glabella-furrows indistinct. Eyes small. Body-rings 

 six : axis arched, very wide anteriorly, but tapering regularly 

 backward. Tail triangular and strongly margined, axis raised and 

 reaching nearly to the hinder margin. This is a very good species, 

 and cannot well be confounded with any other British species. Its 

 small size, very strongly marked tapering axis, and large inflated 

 head, arc good characteristics. 



Discussion. 



Prof. Ramsay was glad to find that the Upper Arenigs mark a 

 passage, as, indeed, he had previously thought. He had never seen 

 volcanic materials in that part of Caernarvonshire ; but intrusive 

 porphyries occur there. It seemed to him that the series was in- 

 complete ; there is no trace of the Tremadoc rocks and Lingula- 

 flags near the Menai Straits, the Arenig beds lying unfaulted upon 

 Cambrian in Caernarvonshire and quite unconformably in Angle- 

 sey. Certain ferruginous beds of the Arenig series which occur 

 near the Menai Straits are found further south lying on Cambrian 

 with no Tremadoc beds or Lingula-flags, and so also in Anglesey. 



Mr. Judd suggested that, in appealing to the case of the Scottish 

 rocks as supporting his views concerning the unconformity between 

 the Cambrian and Silurian formations, Professor Ramsay was 

 reasoning in a circle, seeing that the so-called Cambrian rocks of 

 Scotland had only been identified as such on the ground of their 

 unconformable infraposition to the Silurian. 



Prof. Hughes remarked that the question seemed to be what is to 

 be regarded as the base of the Arenig. The North-Wales district 

 was evidently highly faulted, which gave rise to most of the dif- 

 ficulties. He objected to certain beds being classed as Cambrian 

 without fossil evidence, and maintained that we have as yet no 

 right to apply the term Lauren tian to any rock on this' side of the 

 Atlantic. 



