CLASS III CRINOIDEA 241 



cup and proximale fused ; ventral surface bent to one side. Upper Jura and 

 Lower Cretaceous ; Europe. 



Trigonocrinus Bather. Oxfordian ; Europe. Tormocrinus Jaekel. Small 

 radial facets, rounded interradial spines, and deep cup cavity ; the former has 

 less than five rays. Eocene ; Europe. 



Eudesicrinus Loriol. Stem reduced to two short, thick segments which bear 

 the five R directly. Arms stout, branching on the first brachial. Lias ; Europe. 



■ 



Family 8. Holopidae Zittel. 



Base monocyclic ; stemless. Dorsal cup heaker-shaped, and formed of five fused 

 radials, hy which the body was either directly attached, or more frequently it was 

 supported hy a solid mass representing fused, ^ ^ 



overgrown or absorbed basals. Tegmen com- 

 posed of five large triangtdar orals sur- 

 rounded by a narrow band of perisome. 

 Arms five x two, unhranched, p)innulate, 

 strongly incurving, and composed of large 

 thick plates. Pio. 34(5. 



Of the forms belonging to this family a, b, CotyUdenna docens Oeslongch. upper Lias ; 



Cotylederma Quenst. (Cotylecrinus Des- ^'^^^■,:\^Ti^^''q:^"^^8\ 



long.) (Fig. 346) is found in the Lias: Asselllngen; Baden 'c, Ceutrodorsal ;y, circlet of 

 ri !• 1- n /TXT fused basals. (All tigures of the natuial size). 



tyathidium Steenstrup [Micropocnnus 



Michelin), in the Cretaceous and Tertiary ; and Holopus d'Orb. occurs both in 

 the Tertiary of Italy, and Kecent in the Caribbean Sea, where it inhabits 

 shallow water. 



Range and Distribution of the Crinoidea. 



The discoveries of recent years have brought to light an unexpected 

 profusion of crinoidal life in the present seas, showing that instead of being 

 a decadent and expiring race, as hitherto supposed, the Crinoids still con- 

 stitute a vigoroiis stock of cosmopolitan distribution. They are represented 

 by about 650 species, falling into 100 genera, which are distributed among 

 twenty families and nine additional subfamilies ; about 580 of these species, 

 included in eighty-five genera and in fourteen families and nine subfamilies, 

 are unstalked forms or Comatulids, the dominant type of the present fauna, 

 while about seventy species, included in fifteen genera and six families, are 

 stalked forms. 



The stalked Crinoids attained their maximum development during the 

 Paleozoic era. Three of the principal orders — the Camerata, Flexibilia and 

 Inadunata — are, with the exception of the genus Encrinus, wholly confined to 

 the Paleozoic rocks, although the characteristics of the two last-named orders 

 have continued in more or less modified forms. The Articulata, on the other 

 hand, appear first in the Trias, and are represented continuously to the 

 present time. 



Crinoids, as a rule, have but a very local distribution, but occasional 

 species are common to two continents ; in certain formations detached stem- 

 joints and calyx plates occur so profusely as to become of considerable rock- 

 building importance, and strata aggregating many feet in thickness are fre- 

 quently met with which are almost wholly constituted of Crinoid remains. 

 VOL. I R 



