282 REPORTS OF COMMITTEES. 



Remarks. — The majority of the examples seen on the slab of in- 

 dm-ated shale from Wynyard may be referred without hesitation to 

 C. wrightii. One of the specimens (figs. 2, 2a) exhibits an interesting 

 structural feature at the attenuated and blunt extremity (anterior, 

 auct.), which there is good reason to regard as the rostrum, and beneath 

 this occurs a slender appendage partly hidden below the former, which 

 may be homologous with the antenna. The same wrinkled aspect of the 

 carapace is seen in our specimen, which is common also to those of the 

 Skiddaw slates, indicative of a filmy membranous structure. That 

 this wrinkling is not entirely due to the dynamical folding or rippling 

 of the slate seems to be shown by the fact that the surrounding matrix 

 breaks with a fairly even surface. Further, if we assume that the 

 membranous valves of Caryocaris were strongly inflated in the median 

 area and rigidly strengthened on the dorsal and ventral borders, it is 

 easy to conceive how a flattening of the valve would produce an ex- 

 tremely wi'inkled film. 



C. angusta (a) from the Victorian Lower Ordovician rocks ap- 

 proaches this form very closely, but is distinguished by its rounded 

 anterior. C. wrightii occurs in the Arenig Group in England and 

 Wales (Salter, Jones, Woodward, and Marr), and in the Calciferous 

 (Tremadoc) Group of North America (Gurley). 



Caryocaris marrii, Hicks, ^ee plate, figs. 4, 6. 



C. marrii, Hicks, 1876. Quart. Journ. Geol. Soc, vol. xxxii., 

 p. 138. Jones and Woodward, 1892, Brit. Pal. PhylL, pt. ii., p. 92, 

 pi. XIV., figs. 16-18. 



Remarks. — One of our specimens, smaller and narrower than the 

 preceding species, is probably referable to the above form. The cara- 

 pace in this, like those of the accompanying species, is thin, glossy, 

 and wrinkled. The wrinkling here, however, is as strong longitudinally 

 as transversely. The reproduced outline of one of Jones and Wood- 

 ward's drawings of this form (fig. 6) exhibits the same general shape, 

 but is probably slightly distorted through pressure. It is interesting 

 to note that, similarly with ours, the two species occur together on the 

 same slabs of the Skiddaw slates, and in regard to which Messrs. Jones 

 and Woodward remark that these forms may represent sexual 

 differences. 



Explanation of Plate. 



Fig. 1. — Sifhonotreta maccoyi, Chapman. Example with two 

 valves slightly separated. From glacial erratic, Tasmania, x 5. 



Fig. 2, — Caryocaris wrightii, Salter. Valve showing (?) rostrum, x 2 ; 

 2a. magnified portion of same showing rostrum and (?) antenna, x 5. 

 From glacial erratic, Tasmania. 



Fig. 3. — C. wrightii, Salter. An example of a longer valve with 

 prow-shaped posterior. From glacial erratic, Tasmania, x 2. 



Fig. 4. — C. marrii, Hicks. From glacial erratic, Tasmania, x 4. 



Fig. 5. — C. wrightii, Salter. Outline of Skiddaw specimen, after 

 Jones and Woodward. 



(a) Proc. Roy. Soc. Vict., vol. xv. (N.S.), pt. ii. 1903, p. 113, pi. xvm., fig. 10. 



