ART. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 99 



tests is beautifully pitted. Each of the separated valves is crossed by 

 a nearly vertical fracture, marking, according to Jones, a furrow. The 

 length of the valves is about 9.0 mm., the height about 3.0 rnm. The 

 type specimen was found in the Menevian at St. Davids, Wales. 



This species and Entomis divisa Jones were made the genotj^pes 

 of the new genus Entomidella hj Jones in 1873, although later he 

 regarded E. divisa as the genots^pe, and still later rejected Entomidella 

 I as a synonym of Entomis. That this Cambrian fossil is really a conge- 

 ner of the Silurian Entomis or Entomidella divisa seems highly improb- 

 } able. Throughout his long work on fossil bivalved Crustacea Jones 

 \ was ever too ready to minimize or overlook highly important discrep- 

 j ancies in structure. Numerous instances illustrating this tendency 

 f might be cited. Unfortunately, in the present case, positive data are 

 j lacking; but relying on the illustration and meager notes on E. bupres- 

 I tis published by Jones, there is strong ground for the suspicion that 

 ! the Cambrian species is a very different thing from its supposed 

 : Silurian congener. That the transverse fracture of the valves of the 

 I former represents the long curved furrov/ of an Entomis is especially 

 i' doubtful. It is thought further that the composition of the test, a 

 ! factor apparently never considered by Jones, will prove widely differ- 

 ent in E. bupestris and E. divisa. Until an adequate description of 

 E. bupestris is published the species must remain among the uncer- 

 tain forms. 



A single valve in the United States National Museumi (Cat. No. 

 56501), apparently somewhat compressed vertically and incomplete at 

 one end, is similar in shape and size to E. f buprestis. It was collected 

 by Doctor Walcott at Hanford Brook, St. John County, New Bruns- 

 ' wick, from Cl62 of Matthew's Protolenus zone. Except for the fact 

 that it exhibits no sign of a vertical furrow it might be referred to 

 Salter's species. Possibly it is a distorted and anteriorly incomplete 

 example of Mononotella jusijormis, but the parallelism of its dorsal 

 ! and ventral margins is thought to positively negative that view. For 

 the present it is left unclassified. 



Occurrence. — Middle Cambrian (Menevian): St. Davids, Wales. 

 Doubtfully present in the Lower Cambrian (Hanfordian, C\b2) of 

 ' New Brunswick, 



Genus LEPIDILLA Matthew, 1886 



■ Lepidilla Matthew, Trans. Royal Soc. Canada, vol. 3, sec. 4, 1886, p. 62. — • 

 Miller, North Amer. Geol. and Pal., 1889, p. 553. 



Bivalve? shell having the hinge and body of the valve or plate in 

 different planes. Hinge line straight projecting from the general 

 contour of the shell. Umbo and hinge line separated from the body 

 of the valve by a sinus or emargination behind which is a foramen. 

 (Matthew, 1886.) 



Genotype. — Lepedilla anomla Matthew. Middle Cambrian. 



