64 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



mPPOMCHARION PUCATUM, new species 



Plate 2, Figure 12 



In this new well-marked species the surface between the confluent 

 marginal rim is broken into a series of folds or plications four or five 

 in number and arranged at right angles to the dorsal margin. The 

 ends of the confluent marginal ridge are more strongly marked and 

 appear to be set off as more or less separated elongated nodes. The 

 ridge paralleUng the dorsal margin is slightly developed. Lastly, the 

 outline of the valve is more angular than other species of the genus. 



Occurrence. — Middle Cambrian (Johannian-C26) : McNeil Brook, 

 east of Marion Bridge, Cape Breton, Nova Scotia (3A). 



Holotype.—CAt. No. 81624, U.S.N.M. 



mPPONICHARION PARVUM, new species 



Plate 2, Figure 13 



This, the smallest species of the genus so far discovered, belongs 

 to the section in which the marginal ventral ridges are confluent. It 

 is readily distinguished from its close ally H. plicatum by its more 

 regular outline and more uniformly developed ridges which occupy 

 the space between the confluent marginal elevation. 



Occurrence. — Middle Cambrian (Joliannian, division C2b): One 

 and one-half miles west of Marion Bridge, Cape Breton, Nova 

 Scotia (3i). 



Holotype.— Cat. No. 50551, U.S.N.M. 



raPPONICHARlON CONFLUENS. new species 



Plate 2, Figures 10, 11 



This interesting new species is readily distinguished from the more 

 typical members of the genus by the confluent nature of the marginal 

 ridge, which is entire and not broken, as in the type species. A node 

 and a thin slightly curved ridge are present near the dorsal margin 

 forming a further point of distinction. 



Occurrence. — Middle Cambrian (Johannian, division C2b): One 

 and one-half miles west of Marion Bridge, Cape Breton, Nova 

 Scotia (Si). 



Holotype.— Cat. No. 81625, U.S.N.M. 



Genus POLYPHYMA Groom 



Polyphyma Groom, Quart. Journ. Geol. See. London, vol. 58, 1902, p. 83. 



Carapace bivalved, rather smaU, 2 to 4 mm. in length, semielliptical 

 or semicircular, the hinge long and straight, the ends subequal. Test 

 thin, chitinous, pUable, surface polished, broken up into numerous 



