LOVENECHINUS. 343 



many local peculiarities in this choice specimen which I will now describe. In area A the 

 fifth column originates in a pentagon in the eighth row, with a heptagonal plate on its right 

 ventral border, as usual. In the ninth row there are only four plates, one being a large octag- 

 onal plate, O, whose two extra sides are compensated for by a pentagon above it marked 



5, where the fifth column starts again, and another pentagon, P, below it. Octagonal plates 

 are very rare. In ai-ea C the fifth column originates on the left of the center with a pentag- 

 onal plate having a heptagon in its right ventral border. In the eighth row there is an 

 adventitious pentagon, P, in which the side wanting is compensated for by an adjacent 

 heptagonal plate. In areas E and G the fifth column originates in the sixth row, with a 

 heptagon on the right ventral border, as usual, and in area I it originates in the seventh 

 row, with a heptagon on its right ventral border. In areas A and C there are only five 

 columns of plates, but in the other areas a sixth column is represented by one or two plates 

 in each. In areas E and I a sixth column is represented by one pentagonal plate in the 

 thirteenth or the eleventh row, with a heptagon on its left ventral border. In addition, 

 as a peculiarity, in each area an adventitious pentagon, P, lies on the left of pentagon 



6, and to compensate for the one side wanting, a heptagonal plate, H, lies on the dorsal 

 border of the pentagons. In area G the sixth column is represented by two plates, a 

 pentagon in row 11 and an overlying hexagonal plate. A heptagonal plate lies on the left 

 ventral border of the initial pentagon. In addition, as a peculiarity, an adventitious pen- 

 tagon, P, lies on the right side of hexagon 6, and to compensate for its one side wanting, a 

 heptagon lies on its dorsal border, as in areas E and I. Passing dorsally, column 5 drops 

 out before reaching the apical disc, as seen more clearly in Plate 42, fig. 6. In Plate 41, fig. 1, 

 the plates are drawn representing the character as seen on the proximal or interior aspect of 

 the test, and here all the adambulacral columns extend to the apical disc. As viewed super- 

 ficially, however, a somewhat different condition occurs, as shown in Plate 39, fig. 5; Plate 42, 

 fig. 6. Taking area I as the best example, on the left and right we see the silicified marginal 

 walls of ambulacra J and H, beveling over interambulacrum I. The plates of the adambulacral 

 columns 1 and 2 are existent, but do not reach the surface, being roofed over, or occluded, by 

 the lateral borders of the plates of columns 4 and 3, which alone meet the ambulacra laterally 

 near the surface of the test. This is explained by the diagram (Plate 42, fig. 7), in which on 

 the interior of the test there are five interambulacral plates, but on the exterior only three, as 

 plates of columns 3 and 4 roof over and shut out plates of columns 2 and 1, which therefore 

 meet the ambulacra proximally, but not distally. A similar shutting out of plates quite 

 probably occurs in such a case as Plate 53, fig. 1. A comparable shutting out of plates by 

 occlusion occurs more or less completely in the other areas of the specimen (Plate 42, fig. 6) . 



Dorsally all oculars are in place (Plate 39, fig. 5; Plate 42, fig. 6). The apical disc 

 measures about 16 mm. in diameter, being about 16 % of the diameter of the test which is 



