312 ROBERT TRACY JACKSON ON ECHINI. 



unknown to me in the genus; but Duncan (1889a, p. 14) says the teeth are grooved. Oculars 

 are all insert, or one or more to all may be exsert, being shut out from contact with the peri- 

 proct by the contact of the associated genitals. Genitals are high and wide with several pores 

 each. The periproct is plated with many small thick angular plates similar to those of a 

 Recent cidarid. 



The type species of the genus is M . gigas (M'Coy) from the Lower Carboniferous of Europe. 



Maccoya as a genus occupies a place structurally intermediate as regards the ambulacrum 

 between Palaeechinus and Lovenechinus. The youthful and dorsal localized stages of Maccoya 

 are like Palaeechinus at the mid-zone, and also the character of the plates at the mid-zone of 

 Maccoya is like the secondary youthful and dorsal localized stages of Lovenechinus as set forth 

 in the diagram (text-fig. 237, p. 231). 



Pomel's Wrightella with Palechinus phillipsiae Forbes as the type I do not consider 

 distinct as it has essentially the same structure of the ambulacrum as Maccoya. 1 



Duncan's Palaeechinus used in his restricted sense was intended to cover much the same 

 ground as Pomel's Maccoya, but was more inclusive and embraced some structural types which 

 I refer to Lovenechinus (see pp. 303, 304 and footnote, p. 303). He apparently made a mis- 

 take in taking for Palaeechinus, species which were not covered by M'Coy's original descrip- 

 tion, when there were species that did fall within those limits (Duncan's Rhoechinus). At all 

 events Pomel had priority as first reviser of the old genus Palaechinus M'Coy. 



Key to the Species of Maccoya. 



Four columns of plates in each interambulacral area (America) 



M. burlingtonensis (Meek and Worthen), p. 312. 



Four columns of plates in each interambulacral area (Europe) . . M. intermedia (Keeping), p. 314. 

 Five (?) columns of plates in an interambulacral area M. pMUipsiae (Forbes), p. 316. 



Five to six or seven columns of plates in each interambulacral area, test robust, plates of moderate size 



M. sphaerica (M'Coy), p. 317. 

 Six (?) columns of plates in an interambulacral area, the plates very wide and high 



M. gigas (M'Coy), p. 321. 

 Seven to eight, or exceptionally in part nine, columns of plates in each interambulacral area 



M. gracilis (Meek and Worthen), p. 323. 



* Maccoya burlingtonensis (Meek and Worthen). 

 Text-figs. 10, p. 54; 16, p. 59; 237, p. 231; Plate 32, figs. 1-3; Plate 33, figs. 1-5. 



Palaechinus burlingtoneruns Meek and Worthen, 1860, p. 396; 1866, pp. 230, 231, text-fig. 23, Plate 16, 

 figs. 3a-3c; A. Agassiz, 1874, pp. 648, 649, text-fig. 7; Keyes, 1895, p. 180. 



1 Pomel's Eriechinus and Neumayr's Typhlechinus were both based on what de Koninck described as Palaechinus 

 sphaericus, but it was a mistaken identification and is considered here under Lovenechinus lacazei (Julien), pp. 330-334, 

 text-figs. 240-243; Plate 35, fig. 7. See footnotes pp. 303, 326. 



