52 PROCEEDINGS OF THE NATIONAL MUSEUM vot. 78 



ALUTA FLEXILIS Matthew 



Plate 8, Figures 13, 14 



Aluta flexilis Matthew, Trans. New York Acad. Sci., vol. 15, 1896, p. 198, pi. 15, 

 fig. 4. 



Description. — Carapace acum nate-subovate, oblique, narrow, and 

 angular in front, wide and rounded behind; hinge rather short, an- 

 terior extremity rectangular, postdorsal angle obtuse. Surface 

 features obscured by crushing of valves. A well-defined border 

 beginning at the antero-dorsal angle extends downward around the 

 anterior and ventral sides but is apparently lost on the posterior side. 

 Greatest diameter about 4.0 mm. 



Re7narks.— Only a single specimen of this species is known. This 

 is the original of iMatthew's description and figure of the genus and 

 species and is now preserved in the museum of the University of 

 Toronto. As already mentioned, further preparation of the specimen 

 resulted in proving that it has a straight hinge and is acuminate an- 

 teriorly instead of regularly elliptical in outline. As now under- 

 stood, A. flexilis comes so near to certain Chinese species recently 

 described by Walcott that it is difficult to point out satisfactory 

 differences. Thus A.fragilis {Bradoriafragilis Walcott), which also is 

 founded on crushed examples, differs only in being smaller and in 

 certain minor peculiarities of its outline. Chief among the latter 

 differences is that the hinge is longer in the Chinese species, its pos- 

 terior margin being more nearly vertical than in A. flexilis. In A. 

 eris, A. stereope, and A. woodi, three other small Chinese species of 

 the genus published by Walcott, the posterior outline is more in 

 accord with that of A. flexilis. Each of these species, however, is 

 distinguished by slight differences in the anterior parts of their out- 

 lines. On account of the crushing of the valves of A. flexilis, it is not 

 possible to say whether its surface characters were materially different 

 or not. 



Occurrence. — Middle Cambrian, Acadian division of St. John group, 

 division Clcl, Porter's Brook, St. iMartins, New Brunswick. 



ALUTA BERGERONI (Walcott) 



Plate 8, Figures 3, 4 



Bradoria bergeroni Walcott, Proc. U. S. Nat. Mus. vol. 29, 1905, p. 99. 

 Aluta bergeroni Walcott, Research in China, Carnegie Institution, vol. 3, 1913, 

 p. 225, pi. 23, fig. 10. 



Description. — Carapace obhquely semielliptical, narrow and acu- 

 minate anteriorly, broadly rounded posteriorly, hinge straight, nearly 

 as long as the length of the valve; antero-dorsal angle sharp, 80° 

 or less; post-dorsal angle somewhat obtuse, 100° or more. Surface 

 rather strongly convex, the most prominent point a Uttle behind and 

 above the middle; dorsal slope more abrupt than the ventral. Node 



