35 
Syncyclonema are identical ; if not, there is not the slightest ground for 
uniting them. In the latter case, the whole matter aj^pears to us to he the 
adoption of a previously made suggestion hy Woods, and an assumption hy 
Hind. 
For the purposes of this inquiry we have looked up every reference we 
can find relating to American Syncyclotiemce, and in not one single instance is 
any cardinal structure similar to that of Woods’ figure of the interior of 
P. orbicularis, Shy., either described or figured. We have compared Meek’s 
original definition^ of SyncycIo)iema, Avith Pecten rigida as its type ; the same 
Author’s subsequent remarks' on the species ; the description of the shell 
so referred hy WhitfiehF; "Whiteaves’ description^ of Syncyclonema meekiana, 
and Conrad’s S. simplicia} Moreover, if S. rigida, Wliitfield, the interior of 
wdiich is figured, he S. rigida. Hall and Meek, the two genera are most 
certainly not identical. 
Even previous to IMr. Woods’ suggestion, Syncyclonema was united to 
another genus — Pseudamussium — hy Mr. G. Tryon, Junr.,® 1)iit without 
comment. 
As to Mr, E. Philippi’s remarks, which a])pcar to have been the 
ground for recording the identity of the two genera in (|uestion, the only 
remark of importance Ave can find in his paper “ Zur Stammesgeschichte des 
Pectiniden” is the folloAving passage: — After referring to the near relationship 
of Pntoliuni and Amitssium, he says : “In Pecten discites (Schlotheim, sp., a 
Triassic form), moreover, a character manifests itself AAdiich i.s peculiar to 
the collectiA'c Jurassic Entoliums, hut is particularly strongly shoAvn in the 
Chalk Entoliums, and led Meek to suggest and describe the subgenus 
Syncyclonema, Avhich, as I AAdll later seek to prove, must he merged in 
Entolium”' ; this Ave have not been able to find. So far as Ave understand 
Philippi, the feature that appears to have struck him is the concentric 
sculpture, for, on defining Entolium on a previous page (p. 70), he says : 
“ Smooth, very rarely Avith fine radii, often Avith concentric sculpture 
{Syncyclonema) P 
‘ Meek — Sriiitbsonian Aliscel. C'olhis., 1864, No. 177, ]). 31. 
- Meek — Report U. S. Gcol. Survey Territories (Hayden’s), 1876, IX, p. 27, t. 16, f. .5 n and h. 
’ Wliitfield — Pal. Black Hills Dakota, 1880, p 383, t. 7, f. 1. 
* Whiteaves — Canadian Mes. Foss. 1876, I, Pt. 1, p. 82, f. 9, 
= Conrad — Am. Jonrn. Conch., 1839, Y, Pt. 2, p. 99, t. 9, f. 20. 
Tryon, Junr. — Str. and Syst. Conch., 1884, III, p. 290. 
’ Philippi — Zeitsch. Oeuts. (leol. Gesellsch., 1900, LII, Heft 1, p. 80. 
