450 JENKINS— GEOLOGY OF THE [May 29, 



each ornamented with minute points on its ridge. The specimens 

 are small, about 12 mm. in height and width, and the thickness of 

 the two valves is 6 or 7 mm. Inside casts are smooth and may be 

 confused with the impressions of the sculptured outside. 



CORBULA ( ?) sp. ind. 

 (Plate XX., Fig. i.) 



This Corbula-like form is not like that recorded from Ponta 

 de Pedras. Most of the specimens were 12 or 15 mm. long and 8 

 or 9 mm. high, but one specimen is twice that size. The beak is 

 situated about a third the total length from the posterior end. No 

 radial ribs appear in the impressions, but the lines of growth are very 

 plain, standing out in marked relief. At the anterior end there is a 

 raised portion, almost a ridge, running to the beak. The total angle 

 made by the shell, taking the beak as the vertex, is approximately 

 120°. 



This form is easily recognized by its smooth, even form and 

 the distinct concentric lines of growth. It is abundant at the ex- 

 posure in the railway cut near Itapasaroca, Rio Grande do Norte. 



Cerithium (?) MiRiMENSE Jeukius, new species. 

 (Plate XX., Figs. 8 and 8a.) 

 Many casts and impressions of a Cerithkifn-like form were 

 found at the railroad cut near Itapasaroca, Rio Grande do Norte. 

 The maximum height of the shell is nearly 15 mm. and the width of 

 the lower part is 6 or 7 mm. The angle of the spire is 40° to 45°. 

 Four or five ridges stand out on each half volution, running in the 

 same direction as the spire, and alternate with the ridges on the 

 adjoining volution. Spiral lines, 6 or 7, to each volution, run over 

 the ridges and around the shell, following the volutions, and divid- 

 ing the ridges into a row of little knobs. There are 6 or 7 volutions, 

 which decrease rapidly in size as they approach the top of the spire. 

 The aperture was not well preserved in any of the specimens col- 

 lected. In one or two cases it looks as if it were oval-shaped. 

 There is no sisjn of an extended canal. 



