96 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



ing, linear depressions outline a low, umbonelike elevation. The 

 surface is smooth and polished and slopes more aburptly to the 

 ventral and anterior edges than to the dorsal and posterior margins. 

 The length is given as 0.8 mm., the height as 0.4 mm. 



Occurrence. — Limestone probably Middle Cambrian in age, con- 

 taining besides Acrothele species and Parabolina species. Drift, Neue 

 Brandenberg, Germany, 



DOUBTFUL SPECIES 



LEPIDITTA? AURICULATA Matthew 



Plate 5, Figure 20, Plate 7, Figure 26 



Lepiditla auriculata Matthew, Trans. Royal Soc. Canada, vol. 11, sec. 4, 1894, 

 p. 99, pi. 17, figs. 2a, b; Trans. New York Acad. Sci., vol. 15, 1896, p. 196, 

 pi. 15, figs. 3a, 36. 



The type of this species is most certainly not a congener of the two 

 preceding typical species of Lepiditta. Indeed, it is thought highly 

 improbable that it is a bivalved crustacean at all. Its mode of 

 preservation and general appearance is the same as that of the asso- 

 ciated trilobites, while the form, and especially the symmetrically 

 bilateral arrangement of its parts, suggests nothing else so much as 

 the hypostoma of some trilobite. 



Matthew calls it a left valve and speaks of "two groves in the 

 mold at the hinge line showing that the hinge had two oblique plates 

 or teeth towards the posterior end." The grounds for determining 

 it to be a left valve and not a right are not stated, and close examina- 

 tion has failed to show anything even suggesting such a thing as the 

 supposed hinge teeth. 



Occurrence. — Middle Cambrian (Acadian). In division Clcl of 

 Matthew's section at Hanford Brook, New Brunswick. 



LEPIDITTA? SIGILLATA Matthew 



Plate 5, Figure 21; Plate 7, Figure 27 



Lepiditta sigillata Matthew, Trans. Royal Soc. Canada, vol. 11, sec. 4, 1894, 

 p. 98, pi. 17, fig. 1; Trans. New York Acad. Sci., vol. 14, 1895, p. 138, pi. 8, 

 fig. 8. 



The type and only known representative of this species, while un- 

 questionably one side of a bivalved crustacean, seems no less certainly 

 not congeneric with L. alata. The present shape of the specimen is 

 much like that of a true Lepiditta, but after a careful investigation the 

 conclusion that it resulted through distortion of the dorsal part seemed 

 inevitable. The ventral part of the specimen apparently was not 

 greatly affected, but the back has been crushed and turned, in on 

 itself — a condition that, considering the pliability of the test in most 

 of these Cambrian bivavlves, is not at all extraordinary. Many 



