eine NS ne FNE PMC Nts a? ane Fs “ 7 ‘ , a id an” . 
i Hron . : A 
‘ 
REPORT ON THE CRINOIDEA. 145 
sively through the Jurassic period, and died out in the Lower Neocomian. Their place 
was taken by the Bourgueticrinide, which were formerly associated with them into one 
family. We have no certain evidence of the occurrence of the typical genus Bourgueti- 
erinus in other than Cretaceous rocks; though stem-joints which have been referred to 
this genus occur both in Jurassic and in Eocene deposits. It is not unlikely, however, 
that they belong to Thiolliericrinus or to Rhizocrinus respectively. The latter genus, 
which is represented by two living species, is probably exclusively confined to the 
Tertiary rocks, except perhaps for the so-called Bourgueticrinus alabamensis from the 
Cretaceous formation of Alabama, U.S.; and some of the stem-joints hitherto referred to 
Rhizocrinus or to Bourgueticrinus may possibly belong to Bathycrinus, no calyx of 
which has yet been found in the fossil state. 
As regards the fossil Holopodide, there are Micropocrinus of the Italian Miocene, 
Cyathidium in the Chalk of Faxoe, the singular Gymmnocrinus in the Oxfordien of 
France and Switzerland, and lastly in the Middle Lias Cotylecrinus and Hudesicrinus ; 
while Edriocrinus from the Upper Silurian and Devonian, a type much resembling 
Holopus in character, is a proof of the great antiquity of these sessile Crinoids. 
The Pentacrinidee are remarkable for their long geological history. The type genus 
Pentacrinus first appears in the Trias, together with the short-lived Hnerinus. It per- 
sisted through the whole of the Secondary and Tertiary periods, and is represented by 
eight species at the present time. On the other hand, Hxtracrinus with its characteristic 
stem, dicyclic base, and peculiar arm-divisions is confined to the Lias and Lower Oolites, 
unless, as I am disposed to think, the Pentacrinus asteriscus which has been found in the 
Western Territories of the United States associated with Alpine Trias fossils and Spirifera, 
is also to be referred to this genus. Balanocrinus, known as yet only by stem-joints, 
ranges from the Middle Lias to the Lower Neocomian. The remaining genus Metacrinus 
is confined to Oceania and the shallower parts of the Pacific, and is at present unknown 
in the fossil state. 
The general character of the fossil Pentacrinide is essentially the same as that of 
their recent representatives, except that they often had much longer stems which 
sometimes reached as much as 50 or even 70 feet; while the number of arms was 
frequently limited to ten, which is not the case in any recent species but Pentacrinus 
naresianus (Pls. XXVIII.-XXXa.). Some of them also appear to have been devoid of 
external basals. But in two cases, at any rate, Pentacrinus dixont and Pentacrinus 
fisheri, this is due to error; for the basals have been overlooked and therefore described 
as absent." 
Three genera of the Comatulidze, Antedon, Actinometra, and Hud iocrinus are known 
in the fossil state. The last named is at present limited to the Lower Neocomian of 
1 On the supposed Absence of Basals in the Eugeniacrinide and in certain other Neocrinoids, Ann. and Mag. Nat. 
Hist., 1883, ser. 5, vol. xi. pp. 327-334. 
