On Streptelasnia Frofundum, — -Sardeson. 291 
into two or more species, but on the contrary it becomes 
more evident now than before to me that but one true species 
is represented. Large and small specimens, those with acute 
and with obtnse apices, without and with tabulae all belong- 
together. What is remarkable, however, is that the one spe- 
cies is the only one of the Zap fir ent idea known from either the 
Trenton or Hudson stage. 
Rominger has shown that the winding of the septa seen in 
this species is no longer to be considered as a distinction of 
generic rank among species that are related to this one. The 
genus was originally based upon that character, although 
Edwards and Haime retained the genus only because the}^ ob- 
served no theca which exists in Zap hr en t is. Rominger proved 
also that this, the type species of Streptelasnia has a theca 
but he retained it as a sub-genus. But probably it will be 
ultimately reduced to a synonym of Zaphrentis. I have not 
adopted such a change, however, at this time, since the neces- 
sary study of other species of the same genus and of other ge- 
nera, for that purpose would entail much discussion and more 
than could well be included in one article. If my description 
of Streptelasnia prof miduni prevents the coinage of more un- 
recognizable species or undefined new genera from these mat- 
erials it will have accomplished much. The described manner 
of septal increase which differs in one important respect from 
the law described by Kunth is not considered of subordinate 
importance to the chief aim of this paper. It is a subject 
worthy of special consideration, although, since Kunth (op. 
cit.) has described this coral in particular, when he deduced 
his law for the septal increase among the Tetracoralla, the 
subject is also not inappropriately touched upon in connection 
with this species. 
EXPLANATION OF PLATES XVI AND XVII. 
Plate XVI. 
Streptelasua profundum (Owen). 
1. Side view outline of a large and nearly complete specimen, "S rus- 
ticum.''^ I and ii, points where the increase of septa ceases. Hudson 
formation, Richmond, Indiana. 
2. A specimen of "S*. corniculum.'''' Galena formation, Kenyon, 
Minnesota. 
3. Another specimen of the same showing interrupted growth. 
4. A specimen, "/S\ rufiticum,"' showing a fracture of the corailum at 
a. Hudson formation, Richmond, Indiana. 
