EXDOCEEATIDiE. 
143 
It is well seen also in E. vaginatum, Schloth., sp. None of the 
test is preserved upon the specimen in the National Collection. 
Remark's. This species is well characterized by its exceedingly 
slow rate of increase, and by the large dimensions of its siphnncle. 
Eegarding the first of these features, Eichwald records the measure- 
ments of an example in his own collection, which, in a length of 
9 inches (including 30 chambers), increased in breadth only 2 lines, 
which gives a rate of increase of only 1 in 54. 
Schroder, in his observations upon E. Damesii^ expresses the 
opinion that Schlotheim was in error in comparing E. vaginatum 
with Breyn’s figures (loc. cit.) ; and with this view I quite agree. 
The species described by Schmidt ^ from his “ Schichfc 2 a ” as “ eine 
nahe verwandte Form ” [to “ 0. dujgleoo ”], but with thicker siphunclo, 
occupying half the shell-diameter, and with fiatter chambers, is 
regarded by Schroder as belonging also to E. Damesii^ that is, to the 
species under description. His further conclusion, however, that this 
species is identical with E. vaginatum, is one in which I cannot concur. 
E. vaginatum has a much higher rate of tapering and more crowded 
septa ; in fact, in this respect it is very rarely excelled. Barrande has 
described a species {Endoceras insidare) from the Quebec group (Upper 
Cambrian and Lower Ordovician) of Newfoundland^, which is appa- 
rently an allied form to this one, which it resembles in the large 
size of its siphuncle and slow rate of tapering. E. insidare is cer- 
tainly identical with OrtJioceras [Endoceras'] piscator, Billings, from 
the same country and horizon ^ 
The sculpture of the test of E. complanatum, as described by 
Eichwald, agrees very closely with that of E. rectestrigaium, Schroder, 
and the large siphuncle, numerous septa, and slow rate of tapering 
in the latter add to the similarity between these species, which I 
am strongly disposed to regard as identical. 
Horizon, 0>’//ioc^?’(75-Limestone ( = Arenig). 
Locality. Prussia. 
'Well represented in the Collection. 
Endoceras vertebrale ?, Eichwald. 
1840. Endoceras vertebrale, Eichwald, Ueber das silurische Schicliten- 
system von Ehstland, p. 95. 
^ Archiv fiir die Naturkunde Lir-, Ehst- imd Kurlands, Band ii. Dorpat, 
1858, p. 195. 
^ Syst. Sil. de la Boheme, vol. ii. Texte iii. 1870, p. 721, pi. ccccxxx. ff. 1-11, 
pi. ccccxxxi. ff. 1-10. 
® Palaeozoic Foss, vol i. 1865, p. 251, f. 237. 
