CRINOID FROM THE SOUTHERN SEA. 
931 
Excellent figures of the anal series in Taxocrinus are given by Schultze* * * § and 
Angelin,! while that of Onychocrinus is well represented by Meek and Worthen.^ 
These figures may be advantageously compared with those of Thaumatocrinus on 
Plate 71. 
Since the preceding paper was presented to the Society in April, 1883, the discussion 
between Messrs. Miller and Wachsmuth respecting the nature of Releocrinus has 
been carried on with considerable vigour. 
Stimulated by Miller’s criticisms, Messrs. Wachsmuth and Springer were able 
(with the help of Mr. W. It. Billings) to demonstrate a considerable amount of 
resemblance between Reteocrinus stellaris (Billings), and Glyptocrinus nealli (Hall). 
Both types have (1) the under-basals visible externally, (2) the radials separated 
laterally by the lowest interraclials, which rest on the basals, and (3) a prominent 
median row of plates in the anal interradius ; though Wachsmuth and Springer do 
not lay much stress upon the last point. “ Reteocrinus is readily identified by its 
highly elevated radial ridges, and depressed interradial spaces, filled with numerous 
small plates of irregular arrangement, and extending between the first radials down to 
the basals; by its under-basals, often well developed; its strongly marked bilateral 
symmetry ; and by its ten primary arms as a rule.”§ 
Miller replied by giving a detailed comparison of Glyptocrinus nealli and 
Reteocrinus stellaris, and believed himself to have found such great differences between 
them, “that it is doubtful whether they should even be classified in the same family.”|| 
He lays much stress upon differences in the general aspect of the cup and arms ; a 
little more so, perhaps, than is necessary, considering the poor state of preservation of 
the Canadian specimens. Two points, however, seem to me to be of greater import¬ 
ance. In all the species which have been lately referred to Reteocrinus by Wachs¬ 
muth and Springer, the under-basals are poorly developed, or perhaps even absent ; 
while the third radial is the axillary. But in R. stellaris there are quite large under- 
basals, and the fourth radial is the axillary; and I have some doubt, therefore, as to 
the advisability of referring to this little-known generic type a number of species 
which do not present these characters, more especially the latter one. They all agree, 
however, with Reteocrinus stellaris in a feature which both Wachsmuth and Springer 
and I myself regard as specially distinguishing Reteocrinus from Glyptocrinus, viz., 
* “ Monographic der Echinodermen des Eiflerkalkes.” Denkschr. d. Wiener Akad. Bd. xxvi., 1866. 
Taf. iv., figs. 2, 2b, 3, 4 b. 
f “ Iconographia Crinoideorum,” &c. Stockholm, 1878. Tab. xviii., fig. 8. Tab. xx., figs. 9, 13, 16- 
Tab. xxiii., fig. 5. 
X ‘ Palaeontology of Illinois,’ vol. v., pi. xiv., fig. 4. 
§ “ Remarks on Glyptocrinus and Reteocrinus, two genera of Silurian Crinoids.” Amer. Jonrn. Sci., 
vol. xxv., April, 1883, pp. 265-266. 
|| “ Response to the Remarks of Messrs. Wachsmuth and Springer on the genera Glyptocrinus and 
Reteocrinus." Amer. Jonrn. Sci., August, 1883, p. 112. 
