NOTE ON MEROCRINUS WALCOTT 
13 
richer and better material, might well have led to the complete 
rehandling of my description and speculations. 
It has, however, seemed advisable to print the papers precisely 
as the manuscript left my hands. There will always be some 
value in the exact description of a type-specimen. Moreover 
the divergencies between our two accounts seem to require some 
explanation other than the better preservation of Mr. Springer's 
material. The chief of them are the following. 
The arm-branching is described by Mr. Springer as heter- 
otomous. This is clearly the case in his fig. 5, but it is not quite 
so obvious in his fig. 6. Fragments from the latter specimen 
might have appeared as regularly dichotomous as the fragments 
before me. Therefore I am prepared to admit that there may 
have been slight heterotomy in the hoiotype. In 0. billingsi 
the heterotomy is strongly marked, and, as Mr. Springer says, 
quite peculiar. 
“ The ventral sac, ” writes Mr. Springer, “is composed through- 
out of irregularly hexagonal pieces without any longitudinal 
arrangement.” This statement agrees with his fig, 6 but does 
not appear to be consistent with his fig. 7, which in this respect 
is closer to the hoiotype. It is indeed quite inconceivable that 
the hoiotype can have had a ventral sac like that shown in Mr. 
Springer’s fig. 6. The fragment shown in my fig. 5 may be open 
to some slight doubt, but its structure is consistent with that of 
the main specimen (Plate I, fig. 1) and is quite different from 
that described by Mr. Springer. 
Finally, Mr. Springer lays stress on the presence of “distinct 
plates in the axils between the rays. This is not entirely constant 
in 0. typus, but is observable in the majority of the specimens.” 
Such a plate is shown in his fig, 5. In the hoiotype, at any rate, 
there are no such plates, and the arms are so closely fitted in 
the proximal region that one finds it difficult to imagine the 
appearance of any interbrachials, except, of course, in the anal 
inter radius. 
So much for the differences of description. But examination 
of Mr. Springer’s admirable figures brings to light other differ- 
ences. Thus the proximal region of the stem has not the curious 
wavy structure indicated in my figures 1 and 2. Similarly the 
infrabasals have a pentagonal and not a hexagonal outline. The 
cup seems to widen upwards more rapidly than in the hoiotype, 
and to have more swollen plates. The axillaries are drawn as 
though relatively larger and more nodose than in the hoiotype. 
The stem of 0. typus is not described by Mr. Springer, but that 
of 0. billingsi , which he seems to regard as similar, differs in 
many respects from that of 0. typus hoiotype. 
All these differences lead to the conclusion that the specimens 
referred by Mr. Springer to 0 . typus really belong to a new species, 
