296 THE VOYAGE OF H.M.S. CHALLENGER. 
terminates below in a nodal joint owing to its separation at the syzygy, as is the case 
with so many fossil as well as recent Pentacrimide. Although therefore it seems 
tolerably certain that cirrus-verticils may occur in some species of Hnerinus, the other 
characters of many of the stem-fragments from the Muschelkalk render it equally certain 
that Pentacrinus or an allied genus existed in the same seas as Encrinus. This has long 
been admitted in the case of the St. Cassian beds, which are considerably above the 
horizon of the Muschelkalk ; and they have yielded to Laube* five varieties of Penta- 
crinus-stems, which he has temporarily referred to as many species. Associated with 
these he found one calyx which appears to belong to Pentacrinus; but it was too 
imperfectly preserved for a definite opinion to be formed upon this point. 
All these earlier forms seem to belong to the section of the genus which was desig- 
nated “ Basaltiformes” by Quenstedt, after one of Miller’s species with a pentagonal stem. 
Essentially similar stems are found all through the remaining secondary rocks from the 
Lias upwards, in the Nummulitic Limestones of Biarritz and Kreissenberg, in the London 
Clay, and in the Italian Tertiaries. The calyces associated with them have a monocyclic 
base, and bear simple or dichotomous arms, the two limbs of each fork being of equal 
value, just as in the recent forms. Quenstedt’s other two groups, the Briariden and the 
Subangularen, are those to which the generic name Hxtracrinus was applied by the 
Messrs. Austin. The type is limited in Europe to the Lias and Lower Oolites. Htra- 
crinus briareus appears to occur in the lowest ‘ quick ledge” at Lyme Regis, which 
corresponds to Quenstedt’s lowest bed a; but the type does not reach into the Middle 
Lias, nor indeed into the upper beds of the Lower Lias. In the Jura, however, Hxtra- 
crinus briareus has not been found below the Marlstone (Lias y and 6); but it ranges up 
through the Posidonia-beds, and is said to occur in the Lower Oolites. 
The range of the Subangularen is more limited. They do not occur in the Lower 
Lias of either England or Germany, nor do they reach the top of the Posidonia-beds. 
Many varieties have been made of both species, especially by Quenstedt; but it is note- 
worthy that neither species occurs in all the three divisions of the Lias, Hxtracrinus 
briareus being limited to one only, at any rate in this country. 
Those who have recognised Eztracrinus as a genus, as, for example, Mr. R. 
Etheridge,’ F.R.S., have usually regarded it as limited to the Lias. The Messrs. Austin, 
however, speak of Haxtracrinus briareus as occurring in the Cornbrash at Kingscote Turn- 
pike. They are certainly wrong about the species, but I am very strongly inclined to 
believe that they are correct as regards the genus, and also that the occurrence of the 
Briariden in the Brown Jura (Inferior Oolite), as mentioned by Quenstedt,? is not 
unlikely. 
Die Fauna der Schichten von St. Cassian, Denkschr. d. k. Akad. d. Wiss. Wien., Bd. xx., xxiv., pp. 267-278. 
1 
2 See his Presidential Address to the Geological Society, Quart. Journ. Geol. Soc., 1882, p. 147 (of separate copy). 
5 Eneriniden, p. 270. 
