78 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 87 



depression in the middle of the anterior two-thirds of the dorsal 

 slope. An obscure flattening, caused by a slight elevation of the 

 anterior margin and resulting in a corresponding increase in the gap 

 between the valves, is noticeable on the left valve but not on the 

 right. Test very thin, light brownish to black in color, very minutely 

 and faintly punctate, polished. 



Dimensions of right valve: Greatest (diagonal) length 3.4 mm., 

 greatest horizontal length 3.3 mm., length of hinge 2.0 mm., greatest 

 height 2.7 mm., tliickness about 1.2 mm. Judging from the figure 

 of Matthew's type of L.f primaeva its length is approximately 

 5,1 mm. 



Remarks. — In forming the conclusion that the Hastings Cove 

 specimens are referable to I. primaeva, the right valve shown in 

 Figure 10 on Plate 9 is chiefly relied on. In comparing this valve 

 with Matthew's figure of Leperditia? primaeva, reproduced on the 

 same plate, it will be observed that the former is somewhat wider 

 posteriorly and that the dorsal angles are sharper. These differ- 

 ences, however, may very well be due to incomplete preparation of 

 Matthew's type, a possible criticism for which there has been frequent 

 occasion in the course of the present studies, respecting the original 

 figures of that author's species of bivalved Crustacea. A narrow 

 strip of matrix covering the posterior parts of either the dorsal or 

 ventral edges of the Hastings Cove specimen would cause its exposed 

 parts to agree almost exactly with Figure 9. Even if the type 

 proves to have been perfectly prepared, its apparent peculiarities, 

 regarding its greater size, are scarcel}'^ of sufiicient importance to 

 warrant specific distinction. 



As figured by Matthew, /. primaeva should be closely related to 

 the Grand Canyon species /. faba, which is distinguished solely on 

 the assumption that Matthew's type is not accurately represented by 

 the original illustration. Should this assumption prove ill-founded, 

 then /. faba would become a synonym or variety of /. primaeva 

 (Matthew) (not Ulrich and Bassler) and I. primaeva Ulrich and 

 Bassler (not Matthew), would be subject to renaming. 



Some misgivings may arise in the minds of students concerning 

 the propriety of referring the obviously different left valves to this 

 species. It is done chiefly for the reason that /. matthewi has similarly 

 differing valves. Indeed, these two species are closely allied, differ- 

 ing chiefly in the fact that /. primaeva is relatively shorter. 



Occurrence. — Lower Cambrian (Hanfordian Cl63) at Hanford 

 Brook, St. Martins, New Brunswick. The United States National 

 Museum specimens were collected from apparently equivalent beds 

 at Hastings Cove, Kennebecasis River, about 6 miles east of St. 

 John, New Brunswick. 



Plesiotype.—C'dt. No. 56465, U.S.N.M. 



