182 R. T. JACKSON — STUDIES OF PALiEECHINOIDEA. 



,1 



as showli by the ventral area of the same. In this feature it, as well as 

 Melonites multiporus, is like the adult of Oligoporus ; later these columns in- 

 crease to 12. This is a hi(j;her number than is attained b}'' any other species 

 of the genus except Melonites etheridgii, W. Keeping* (see systematic 

 table facing page 242). In the adult, Melonites giganteus has more col- 

 umns of interambulacral plates than Melonites multiporus or any species 

 of the genus. It ma}^, then, in this salient feature be considered the ex- 

 treme species of the genus, being furthest removed from the ancestral 

 stock, which must have had relatively few columns, as evidenced by the 

 stages in growth through which it has passed. To put it in other words, 

 when very young it had at most 3 columns, then 4, like Melonites dispar, 

 (Fischer), and next 5 columns, which is characteristic of adult Melonites 

 crassus, Ilambach ; when older still it had 7, then 8, like adult Melonites 

 multiporus; later 9 columns like extreme cases of Melonites mid tipor^ts ; 

 finally it goes ahead of anything found in other species, and has 10 and 

 11 columns.t 



In the accompanying table are shown the relations and form of the 

 plates in the several interambulacral areas of our specimen as far as they 

 could be ascertained. In studying this table comparison is requested 

 with the figures of this species, with the tables of Melonites multiporus 

 (pages 165-170 ; see also page 161), and with the figures of other species 

 and genera of Paleozoic echinoids illustrated in the accompanying plates ; 

 also it should be considered in connection with the S3^stematic table of 

 classification of Paleozoic Echini, facing page 242. 



DESCRIPTION OF MELOXITES SEPTENARIUS, SP. NOV. (R. P. WHITFIELD). 



Plate 9, figure 49. 



In the American Museum of Natural History in New York, there is a 

 specimen of Melonites from the Warsaw group, 8ubcarl)oniferous, of Buz- 

 zard Roost, Franklin county, Alabama, lower limestone. No specimens 

 of Melonites have been previously recorded from the Subcarboniferous 

 of the south Atlantic states. This species differs from any previously 

 described, and for it Professor R. P. Whitfield suggests the name Melo- 

 nites srptendrins, the name indicating the number of columns of plates in 

 the interambulacral area. The specimen (plate 9. figure 49) is a silicified 

 cast from the interior, but in ])arts shows the original thickness of the 



*The type of this species is in the Museum of Practical Geology, Jermyn street, London. 



t In the collections of the Wagner Free Institute at Philadelphia there is a specimen, catalogue 

 number 5255, which is ascribed to the species Melonites gir/anteus. It is from the Sub-carbonifer- 

 ous of Tennessee. The specimen, which is fragmentary, corresponds in details of size and pro- 

 portions with the type. In the ambuhxcrum there are 12 columns of plates, but in the interam- 

 bulacrum there are but 9. Ten rows of plates are added, after the introduction of the ninth 

 column, without the introductioA of a tenth column. This fact is a striking difference from the 

 type, as described above. 



