LOVENECHINUS. 339 



presents a continuous curve corresponding with the rest of the test (Plate 39, figs. 4, 5), instead 

 of being arched up in the center. Demi- and occluded plates are of about equal width (Plate 

 43, fig. 4) instead of the occluded being wider, and pore-pairs are close to the middle line of each 

 half-area instead of lying near to the next adjacent interambulacrum (compare Plate 43, figs. 

 1, 2, and 3, 4). Demi-plates opposite horizontal interambulacral sutures are broad and fan- 

 shaped. This is not a specific, but a generic and family character, seen also in Melonechinus 

 (Plate 56, fig. 5, p. 360). 



The interambulacra are wide, and at the mid-zone consist of five columns of plates in each 

 area (Plate 39, fig. 3; Plate 44, figs. 2-4; Plate 46, fig. 4), or occasionally a sixth column in 

 addition may be represented by from one to three or more plates in an area, but in no specimen 

 seen does this extra column occur in all areas (text-fig. 244; Plate 40, fig. 1, area I; Plate 41, 

 fig. 1, areas E, G, I). The adambulacral plates are pentagonal, beveled under the ambulacrals 

 on the adradial suture, this inclined face bearing curved facets for articulation with the demi- 

 plates. Occluded plates on the interior do not touch the adradials, as they do in Maccoya 

 (Plate 34, figs. 2, 3). The median columns are composed of hexagonal plates excepting where 

 new columns come in, and also excepting local irregularities as the plates marked P, in text-fig. 

 244, and Plate 41, fig. 1. The interambulacral plates are thick, but not nearly so much so, or 

 so massive as in the nearly related Lovenechinus nobilis. The surface is thickly studded with 

 small secondary tubercles like those of the ambulacra, but spines have not been observed in 

 this species. In the interambulacra ventrally there are two plates in the basicoronal row (Plate 

 43, figs. 1,2), above which there are three plates in the second row, and four in the third, the 

 fifth column coming in later at somewhat variable intervals as shown in the figures cited and 

 on Plate 41, fig. 1. In a relatively young specimen (Plate 39, figs. 1, 2; Plate 40, fig. 1) the 

 fifth column in four areas originates near the mid-zone, but there are many fewer rows than 

 in an adult (Plate 41, fig. 1), in which the same column, appearing at about the same age, 

 is pushed adorally in virtue of the fact that many more rows have been added dorsally. 



The peristome is unknown. The apical disc is relatively small in the several specimens 

 measured. Its diameter in mature individuals proportionately is about 16 to 18 % of the 

 diameter of the test. In the young individual (Plate 39, fig. 1) the apical disc is proportionately 

 larger, as usual in young Echini, being about 21 % of the diameter of the test. Oculars are 

 usually all insert and cover the ambulacra and laterally the interambulacra in part on either side 

 (Plate 39, figs. 3, 5; Plate 41, fig. 3; Plate 42, fig. 6). As seen in several of the oculars figured, 

 there is on these internal molds an elevated siliceous plug, near the adoral margin, which 

 apparently represents a cast of an ocular pore. An ocular pore has not been seen on the ex- 

 terior in any species of this family, and whether these pores would have reached the surface is 

 doubtful (p. 89). In one case, the young specimen, two oculars are exsert, being excluded 

 from the periproct by the contact of the two adjacent genitals (Plate 41, fig. 2). The geni- 



