XI. Balanucrinus. 405 



Summary axd Conclusions. 



All the specimens from Biarritz to which d'Arcliiac and 

 others have applied the name Pentacrinus didactylus belong 

 to a single species. 



Examination of normal adult joint-faces shows that that 

 species falls within the genus Balanocrinus as ordinarily 

 understood. 



The specimens from the London Clay to which the names 

 Fentacrinus suhbasaltiformis and P. soiverbii have been 

 applied, with the exception of a few fragments erroneously 

 determined, may be assembled in a series that falls within 

 limits of variation no greater than those of B. didactylus, 

 and in some respects even less. Therefore those specimens 

 all belong to a single specieg. 



That species also belongs to Balanocrinus, though the 

 chai'acteristic features are less pronounced. 



The Biarritz species and the London Clay species are, 

 however, distinct from one another, and must be known 

 respectively by the names Balanocrinus didactylus d^Archiac 

 ex d^Orbigny, and Balanocrinus subbasaltiformis J. de C. 

 Sowerby ex Miller. 



Sowerby's figure 3 b (Brit. Mus. 57539), supposed by him 

 to represent a cirrus of P. subbasaltiformis ^ is a stem oL' 

 Isocrinus character with a pentagonal section actually visible- 

 in Sowerby^s engraving. It appears to be the stem of the 

 later-described Cainocrinus tintinnabulum Forbes. 



Pentacrinus dixoni Ooster, may be the same as Balano- 

 crinus didactylus, but Ooster's name must form the subject 

 of a separate note. 



Pentacrinus diaboli Bayan, wdiich Meneghini referred to 

 B. didactylus as interpreted by him, is an alternicirrate 

 Balanocrinus, with 2 & 3 facets to the whorl, but differs in 

 its marked pentagonal section and other respects from 

 d^Archiac's species (Brit. Mus. E 22032-22052). 



Pentacrinus lorioli Noelli (1900, Atti Soc. Ital. Sci. Nat., 

 xxxix. p. 28, pi. i. figs. 33, 34), based on cylindrical stem- 

 fragments from the Upper Helvetian of Piedmont, was 

 referred by me to Balanocrinus in the ' Zoological Record ' 

 for 1900 (1901), by reason of its joint-face, which Dr. Noelli 

 himself compared with that of B. bronni. The " due in- 

 fossature molto distinte '^ on what is presumably the 

 hypozygal indicate that the stem was alternicirrate. 



Pentacrinus subbasaltiformis Miller, var. subrotundus 

 De Gregorio (189i, Ann. Geol. et Pal., Livr. 13, p. 17, pl.ii. 

 figs. 41, 42), from the Bartonian of Valrovinaj may be 



