PER.— PIS.] 



ECHINODERMA TA. 



269 



plates imbricating upward, and from 

 the center outward ; primary spines on 

 the rows adjoining the ambulacra, the 

 supporting tubercle being small, per- 

 forated, but not crenulated, and sur- 

 rounded by a double ring ; ovarian 

 plates having 6 pores; mouth and anal 

 openings small, central. Type P. 

 biserialis. 

 illinoisensis, Worth en & Miller, 1883, 

 Geo. Sur. 111., vol. 7, p. 333, Kas- 

 ka-kia Gr. 



Pereiochocrinus, Austin, 1843, Ann. and 

 Mag. Nat. Hist., vol. 11, p. 203. Not 

 defined so as to be recognized, though 

 some authors use it instead of Sacco- 

 crinus. 



Petkaster, Billings, 1858, Can. Org. Rem., 

 Decade 3, p. 79. [Ety. petros, stone ; 

 aster, star.] Closely related to Palseas- 

 ter, and having both marginal and 

 adambulacral plates, with a Jew disk- 

 plates, on the ventral side. Type P. 

 rigidus. 



Fig. 389.— Pelrnsterbellulus. 



bellulus, Billings, 1865, Pal. Foss., vol. 1, 

 p. 393, Niagara Gr. 



rigidus, Billings, 1857, (Palaeasterina rig- 

 idus,) Rep. of Progr. Geo. Sur. Can., p. 

 291, and Can. Org. Rem., Decade 3, p. 

 80, Trenton Gr. 



wilberianus, see Palseaster wilberanus. 

 Philocrinus, Koninck, 1863. [Ety. philos, 

 favorite ; krinon, lily.] 



pelvis, Meek & Worthen, 1865, Am. Jour. 

 Sci., 2d series, vol. 39, syn. for Eriso- 

 crinus typus. 

 Pholidocidaris, Meek & Worthen, 1869, 

 Proc. Acad. Nat. Sci. Phil., p. 77. [Ety. 

 pholidos, scale ; kideris, turban.] Inter- 

 ambulacrals thin, irregular, imbricating 

 upward and laterally ; five or more 

 rows ; only two reaching the extremi- 

 ties ; marginal rows and those on the 

 lower side having primary tubercles, 

 showing a pit in the top, and being 

 surrounded by two rings; ambulacral 

 areas wide, with six or more rows of 

 plates imbricating downward,, each 

 plate pierced by two pores, and the 

 larger ones having additional pores. 

 Type P. irregularis. 



irregularis, Meek & Worthen, 1869, Proc. 

 Acad. Nat. Sci. Phil., p. 78, and Geo. 

 Sur. 111., vol. 5, p. 512, Keokuk Gr. 



Physetocrinus, Meek & Worthen, 1869, 

 Proc. Acad. Nat. Sci. Phil., p. 158. 

 [Ety. physetos, inflated ; krinon, lily.] 

 Distinguished from Actinocrinus, in 

 the form and construction of the vault, 

 which has no proboscis, and has pores 

 along the radial portions of the dome; 

 and, also, in having no hook-like pro- 

 jections along the pinnules. Type P. 

 ventricosus. 



asper, Meek & Worthen, 1869, Proc. 

 Acad. Nat. Sci. Phil., p. 161, and Geo. 

 Sur. 111., vol. 5, p. 351, Burlington Gr. 



c o p e i , S. A. 

 Miller, 1881, 

 ( Actinocrinus 

 copei,) Jour. 

 Cin. Soc. Nat. 

 Hist., vol. 4, p. 

 310, Burling- 

 ton Gr. 



dilatatus, Meek 

 & Wor then, 

 1869, (Stroto- FlG 390. _pi iyse tocrinus 

 cnnus dilata- copei. 



t us , ) Pro c . 



Acad. Nat. Sci. Phil. p. 162, and Geo. 

 Sur. 111., vol. 5, p. 363, Burlington Gr. 



ornatus, Hall, 1858, (Actinocrinus or- 

 natus,) Geo. Sur. Iowa, p. 583, Burling- 

 ton Gr. 



reticulatus, Hall, 1861, (Actinocrinus 

 reticulatus ) Desc. New Crin., p. 3, 

 Burlington Gr. 



subventricosus, McChesney, 1860, (Acti- 

 nocrinus subventricosus,) Desc. New 

 Crin. Pal. Foss., p. 21, and Trans. Chi. 

 Acad. Sci., p. 16, Burlington Gr. 



ventricosus, Hall, 1858, (Actinocrinus 

 ventricosus,) Geo. Sur. Iowa, p. 595, 

 Burlington Gr. 



ventricosus var. cancellatus, Hall, 1861, 

 (Actinocrinus ventricosus var. cancel- 

 latus,) Bost. Jour. Nat. Hist., vol. 7, p. 

 279, Burlington Gr. 



ventricosus var. internodus, Hall, 1861, 

 (Actinocrinus ventricosus var. inter- 

 nodus,) Bost. Jour. Nat. Hist., vol. 7, 

 p. 278, Burlington Gr. 

 Pisocrinus, DeKoninck, 1858, Bull. Acad. 

 Roy. Belgique, 2me ser., tome 3, p. 24. 

 [Ety. pisos, pea; krinon, lily.] Calyx 

 round globular ; basals 5, forming a 

 triangle ; these are followed by three 

 large plates, forming nearly the entire 

 calyx; one of these supports two small 

 plates, and a small plate is supported, 

 in a notch, between the other two 

 larger plates; arms 5; column round. 

 jam* Type P. pilula. ^ 



■*k f^Dl gemmiformis,S. A. Miller, 



\ZP 1879 » Jour - Cin - Soc - 



Fl G.391.-Pi S ocri- f^^L'*^ 1 - 2 ' P ' 



nus gemmifor- no, lMdgdra, vji . 



mis. Natural glob os us, Ringueberg, 



• sizeandmagni- ig84, (Triacrinus glob- 



osus,) Proc. Acad. Nat. 



Sci. Phil., p. 146, Clinton Gr. 



