46 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



Occurrence. — Lower Cambrian (Hanfordian, division Cl6l-Cl63): 

 Hanford Brook, New Brunswick. 



Plesiotypes.— Cat. No. 50491, U.S.N.M. 



BEYRICHONA ROTUNDATA Matthew 



Plate 6, Figure 12; Plate 7, Figures 11, 12 



Beyrichona rotundata Matthew, Trans. New York Acad. Sci., vol. 14, 1895, 

 ' p. 136, pi. 7, fig. 9. 



Represented in the Matthew collection by three specimens. Two 

 of these, A and B, are alike, the third, C, not entirely clear of the 

 matrix, seems to be a more triangular form than the other tv/o, 

 and probably is referable to B. tinea, or possibly the young of B. tinea 

 planata. 



Specimens A and B agree fairly well with Matthew's figure, except 

 that the free border is scarcely so uniformly rounded as represented 

 in the figure. As to the validity of the species, it is closely related 

 to tinea and planata, differing from both in the lesser height of the 

 valves and more uniformly curved ventral margin. Except that the 

 sulci are deeper, the configuration of the dorsal half of B. rotundata 

 corresponds in all essential respects with B. tinea, and differs, there- 

 fore, the same as that form, from B. planata. Possibly this form 

 also is but a variety of B. tinea, but if the peculiarities shown in the 

 types are fairly constant, it will be best to class it as closely aUied 

 but specifically distinct. 



Occurrence.— J jOwbt Cambrian (Hanfordian, division Clb2, Cl63): 

 Hanford Brook, New Brunswick. 



Plesiotype.—C&t. No. 50500 U.S.N.M. 



BEYRICHONA TRICEPS (Matthew) 



Plate 6, Figures 13-15 



Beyrichia triceps Matthew, Geol. Surv. Canada, Rept. Cambrian Rocks Cape 

 Breton, 1903, p. 219, pi. 16, figs. 4c-4c. 



Though resembUng the Silurian genus of Ostracoda in general 

 aspect, this species is no more a Beyrichia than are the other Bra- 

 doriidae and Beyrichonidae. The type specimens are all more or 

 less imperfect, but between them they leave no doubt in our minds 

 that the species belongs strictly to Beyrichona. In essential features 

 it differs from the typical species solely in being relatively elongate. 

 The nodes, especially the central one, are somewhat stronger in 

 B. triceps, but this is to be expected as a natural result of the vertical 

 shortening. 



The greater the proportionate height (see Escasona) the less dis- 

 tinctly developed are the nodes. 



