EOCENE echinodeemata. 149 



Genus ECHINOLAMPAS Gray. 



ECHINOLAMPAS APPENDICULATUS Emmons. 



Plate LXVIII, figures 2a-h. 



Echinolampas appendiculatus Emmons, 185S, Agriculture Eastern Counties: North Carolina Geol. Survey Rept., p. 307, 



figs. 240, 241. 

 Echinolampas appendiculatus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 697. 



Determinative characters. — Test suboval to subovate in marginal outline, broad and rounded 

 anteriorly, narrowing in nearly straight lines to the pointed, obliquely truncated posterior end; 

 sides and anterior end rounded and inflated. The upper surface convex, depressed, and usually 

 rather flat on top, with a tumid, rounded ridge over the periproct; under surface very tumid 

 for a wide area around the margin, slightly concave near the peristome. Apex central or sub- 

 central. Ambulacral areas narrow, dorsal portions petaloid; petals narrow, some with porifer- 

 ous zones unequal in length. Apical system excentric anteriorly. Peristome large, elliptical, 

 transverse, excentric anteriorly, with an inconspicuous floscelle. Periproct large, subelliptieal, 

 inframarginal, beneath the protruding posterior ridge. 



Dimensions. — The figured form, which is about average size, gave length 33 millimeters; 

 width 28 millimeters; height 17 millimeters. The largest specimen gave length 48 millimeters; 

 width 42 millimeters; height 23 millimeters. 



Description. — This species was described and figured by Emmons in 1858. It appears to 

 be limited to North Carolina, where it is often found in association with Cassidulus carolinensis. 

 In actual number of specimens it is the most abundant of the Cenozoic Cassiduloidea occurring 

 in the United States, the writer having had more than 300 specimens available for study. The 

 writer has also had the privilege of studying Emmons's type, which is in the collection of Williams 

 College; and as a result has determined that in applying the name "appendiculatus" to the 

 species based upon the " subcordate sculptured plate with a pentagonal opening, in the center of 

 which there is a pore" which was said to occupy the apical disk, Emmons made a curious mis- 

 take. His type does show a plate of some such character as he described but it is evidently 

 foreign to the test, probably a fragment of some other fossil — possibly the plate of some cidaroid 

 form — which has by accident become cemented to the test in the neighborhood of the apical 

 system. Emmons's type is the only one of the 300 specimens examined by the writer which 

 possesses any such plate. Furthermore, it is difficult to conceive of any possible function for 

 such an appendix to an echinoid test. This species is somewhat variable in minor details, but 

 its broad characteristics are quite uniform and easily distinguished. The test is thin walled, 

 depressed-ovoid in general form; marginal outline suboval to subovate, rounded anteriorly, 

 broadening back of the middle, then rapidly narrowing in almost straight, converging fines to the 

 rather pointed, somewhat rostrate posterior end; margin very round and highly inflated, less 

 so along the narrowing part on both sides of the posterior end, and downwardly and anteriorly 

 truncated at the posterior end. The upper surface is usually rather low, regularly convex, 

 depressed, rather flat on top and in the form of a tumid rounded ridge over the periproct; 

 though occasional specimens are moderately elevated, and somewhat ridged along the whole 

 longitudinal median area; under surface very tumid for a wide area around the margin, 

 slightly concave near the peristome. The apex is central or subcentral. 



The ambulacral areas are narrow, dorsal portions petaloid; petals narrow, rather long, 

 varying somewhat in details on the same specimen and from specimen to specimen, the posterior 

 pair usually slightly longer than the anterior three, which are nearly equal in length, partly open 

 at their extremities. The poriferous zones are narrow, flush, the inner zones of the posterior 

 petals slightly shorter than the outer zones, and in a less degree the anterior zones of the anterior 

 paired petals shorter than the posterior zones; outer row of pores oval, inner row round; pairs 

 of pores conjugate, the ridges between the pairs of pores prominent and ornamented with a row of 

 granules. 



The surface of the test is highly ornamented. There are numerous small tubercles in wide, 

 deep scrobicules. On the under surface the scrobicules are more numerous, different in size and 



