REPORT ON THE CRINOIDEA. 299 
recent types that when allowance is made for the different stages of growth, the 
characters of the stem are of much use in the distinction of species. This is especially 
the case if the number of internodal joints can be ascertained, which is not often possible, 
however, with fossil stems. But I am more disposed than I formerly was to accept 
the numerous species described by de Loriol and Quenstedt on the characters of the stem 
alone. Under these circumstances it is possible that more of the Continental species 
may eventually be found to occur in Britain, the number at present known being very 
small. 
The geological range of individual species, both of Pentacrinus and of Extracrinus, 
seems to be rather limited, no species occurring in all three divisions of the Lias. Out of 
fifteen species of Pentacrinus which are found in the Middle and Upper Lias of Britain, 
only two are common to the two horizons. Neither of the two Lower Lias species reach 
the Middle Lias, though Pentacrinus basaltiformis dogs so on the Continent. This and 
Pentacrinus psilonoti axe the only Continental species which have yet been recognised in 
the British Lias. One species of the Kimmeridge Clay, Pentacrinus sigmaringeisis, also 
oceurs in the White Jura of the Continent. 
This agrees very well with the geographical distribution of the Pentacrinide in the 
recent seas, the four West Indian species, though abundant in the Caribbean Sea, not 
occurring elsewhere ; while the remaining two Atlantic species have respectively been found 
at one and at three stations only. Pentacrinus naresianus was obtained in the West 
Pacific in lat. 29° 55’ S., and also in lat. 4° 33’ N. (or possibly 9° 26’ N.), and has the 
widest geographical range of any Pentacrinus, recent or fossil, that I am aequainted with. 
Like the Silurian Crinoids, therefore, the species of Pentacrinus, both recent and fossil, 
seem to be somewhat limited in their geographical range. 
The genus has, however, a wider geographical range than Metacrinus, which is 
confined to the Pacifie Ocean and the East Indian Archipelago. On the other hand, 
while fourteen species of Metacrinus are known, Pentacrinus is only represented by eight, 
together with the doubtful form which I have called Pentacrinus (?) mollis (Pl. XXXIT. 
figs. 7-10). The mutual relationships of these eight species are shown in the 
followmmg table; and it will be seen that they fall into two very natural groups, 
which have the four Caribbean and the two Pacific species equally divided between 
them. 
