XI. Balanocrhms. 387 



brouglit from Biarritz by Mr. S. P. Pratt, on which the 

 Austius founded their P. prattii, and it is these which foriu 

 the basis of the present study. They are registered E 219i3- 

 E 2.2028. 



The first question to settle is the generic position of the 

 species. In 1888, when arranging the Tertiary crinoids in 

 the Geological Department of the British Museum, I labelled 

 the specimens of this and some other species as Balanocrinus, 

 a genus which previously had not been recognized later than 

 the Cretaceous period. It does not, however, appear that 

 this ascription has ever been published in so many words, 

 and down to quite recent years geologists continued to refer 

 to the Biarritz fossil as Pentacrinus didactylus. Of course, 

 it is not a Pentacrinus sensu strict© ; what these writers 

 mean is Isucrinus (see ' Pentacrinus : a Name &c.,' Natural 

 Science, xii. p. 2i5, April 1898). 



^ Characters of Balanocrinus. — This section was separated 

 from Isocrinus by de Loriol, first as a subgenus (1879, 

 ' Monogr. Crin. foss. Suisse'), subsequently, with the 

 approval of P. H. Carpenter, as a full genus (1889, ' Paleont. 

 Franc., Jurassique, Crinoides,' part 2, p. 295). The dia- 

 gnostic characters were drawn solely from the stem, no other 

 portion being then known with certainty. Translated into 

 modern terminology (see Bather, 1909, 'Trias. Echin. 

 Bakony/ pp. 21-30) and revised, they are as follows : — 



Transverse section varies usually from circular to penta- 

 gonal, and rarely to somewhat quinquelobate. Side-faces 

 usually smooth, but may be granulate. A radial depression 

 and pore sometimes present. Normal joint-face with peri- 

 pheral crenellae short, tending to form a continuous series 

 of subequal crenellae round the margin ; with adradial 

 crenellae opposite and set at right angles to the perradius, 

 but always reduced in size, often to mere granules, and thus 

 forming single or double rows passing along the perradius 

 from the central area to the crenelate periphery. Thus the 

 petal-floors are separated from each other by straight 

 boundaries. Syzygial joint-face frequently with peripheral 

 crenellae reduced in size and adradial crenellae similarly 

 reduced or replaced by a single linear groove along each 

 perradius, with floors smooth and on the epizygal often 

 raised. Cirrus-facets transversely elliptical, as in Iso- 

 crinus. 



A tine series of figures was given by de Loriol (1887-88, 

 ' Paleont. frang.,' torn. cit. pis. clxxxii.-cxcvii.). 



Genotype. — Pentacrinites subteres Miinster, in Goldfuss, 



2tJ* 



