HBT. — HOI,.] 



ECHINODERMA TA. 



253 



Hetkrocystites, Hall, 1852, Pal. N. Y., vol. 

 2, p. 229. [Ety. heteros, irregular ; kustis, 

 bladder.] Basals 4, irregular in size ; 

 second series 10, large; higher plates 

 numerous, but exact order and number 

 undetermined. Type H. armatus. 

 armatus, Hall, 1852, Pal. N. Y., vol. 2, p. 

 229, Niagara Gr. 

 HETEROscHisMA,Wachsmuth, 1883, Geo. Sur. 

 III., vol. 7, p. 352. [Ety. heteros, irregu- 

 lar; schisma, slit] It is distinguished 

 from Codaster by the sunken bydro- 

 spiral areas and ex- 

 posure of the orals, 

 only, immediately 

 contiguous to the 

 mouth ; the limbs 

 are extended inter- 

 radially, into pyra- 

 midal ridges, which 

 the hydrospires en- 

 ter obliquely. Type 

 H. gracile. 

 alternatum var. elon- 

 gatum, Wachsmuth, 

 1883, Geo. Sur. 111., 

 vol. 7, p. 354. 

 Founded upon a 

 magnified view of 

 Codaster attenuatus. 

 gracile, Wachsmuth, 1883, Geo. Sur. 111., 

 vol. 7, p. 354, Ham. Gr. 



Fig. 330.— Hetero- 

 sc his in. 'i gracile. 

 Side view, 3diam. 



Fig. 331.— Heteroschisma gracile. Horizontal 

 section of nydrospires, 5 diam. 



Holocystites, Hall, 1864, 20th Rep. N. Y. 

 St. Mus. Nat. Hist., p. 353. [Ety. holos, 

 entire; kustis, bladder.] Body cylin- 

 drical, subovate or globose, free, sessile, 

 or attaching by roots, and covered by 

 numerous ranges or irregular series of 

 larger and smaller poriferous plates ; 

 ambulacral opening central or sub- 

 central; mouth excentric ; smaller open- 

 ing between these ; arms mere spinous 

 processes. Type H. cylindricus. 



abnormis, Hall, 1864, 20th Rep. N. Y. St. 

 Mus. Nat. Hist., p. 355, Niagara Gr. 



alternatus, Hall, 1861, (Caryocystitesalter- 

 natus,) Rep. of Progress Geo. Sur. Wis., 

 p. 23, and 20th Rep. N. Y. St. Mus. Nat. 

 Hist., p. 355, Niagara Gr. 



baculus, S. A. Miller, 1879, Jour. Cin. Soc. 

 Nat. Hist., vol. 2, p. 105, Niagara Gr. 



brauni, S. A. Miller, 1878, Jour. Cin. Soc. 

 Nat. Hist., vol. 1, p. 130, Niagara Gr. 



canneus n. sp. 

 Niagara Gr. 

 Body long, ir- 

 regularly sub- 

 c y 1 i n drical ; 

 summit pro- 

 longed on the 

 flattened side 

 in the direc- 

 tion of the 

 ambulacral 

 orifice ; plates 

 long, polygo- 

 nal, of irregu- 

 lar size; eight 

 ranges may be 

 counted in 

 our specimen, 

 and one or 

 two have 

 been broken 

 from the 

 lower end ; 

 the ambula- 

 cral orifice is 

 su r rounded 

 by six plates ; 

 below this 

 there is a 

 range of eight 

 plates, three 

 of which 

 reach the mouth, and one of which bears 

 the anal orifice ; there are no arms, am- 

 bulacral spines, or cicatrices ; there are 

 eight plates in the next range, two of 

 which join the mouth ; the mouth in 

 this genus is generally upon the flat- 

 tened side of the specimen and opposite 

 the posterior bulge, but not so in this 

 species, for the ambulacral area is pro- 

 longed on the flattened side, and the 

 bulge is opposite thereto, while the 

 mouth is on the side of the summit be- 

 tween the bulge and the flattened side ; 



Fig. 332.- 



Holocystites can- 

 neus. 



Fig. 333.— Holocystites canneus. Summit view. 



all the plates are very poriferous, the 

 pores penetrating the plates in clusters 

 of from two to seven instead of by pairs 

 as is usual in this genus ; the flattened 



