172 PROF. P. M. DUNCAN ON STREPTELASMA REMERI, 
with the median line of a septum, the mural character of the outside 
structures is quite evident. 
Messrs. Nicholson and Etheridge remove the genus Streptelasma 
from the Cyathophyllidz into the Zaphrentide. I quite agree with 
their able arguments; and it is clear that the costulation of the 
forms mentioned in this communication strengthens their views; 
for a single pinnation is to be observed in some species of Zaphrentis, 
and the straight costz are then seen in relation with the septal 
fossula. 
The new species should be placed at the end of the Streptelasmata ; 
and it approaches the simple Rugosa with uninterrupted interseptal 
loculi. Probably the Upper Silurian is the highest horizon on which 
the Streptelasmata will be found, and the genus flourished in the 
Lower Silurian in America. 
Nore, January 1884.—Lindstrom, in his ‘ Index to the Generic 
Names applied to the Corals of the Paleozcic Formation,’ Stockholm, 
1883, gives Ptychophyllum, Kd. & H., 1850, as synonymous with 
Streptelasma. Now the diagnosis of Ptychophyllum is as follows :— 
“ Corallum simple, pedicellate, mainly constituted by a series of 
superimposed subinfundibuliform tabulze (planchers), and whose 
surface presents numerous septal rays tolerably equally developed ; 
these rays are strongly twisted near the centre of the tabule, so as 
to form a false columella” (Hist. Nat. des Corall. vol. ii. p. 399, 
1860). Certainly there is a very considerable distinction between 
the two genera; and I retain the original genus as diagnosed 
by Hall, with a slight modification. The close similarity of costal 
structure in Hadrophyllum conicum and Zaphrentis Candez of 
C. Barrois (species from the Devonian of the Asturias and Galicia, 
Spain), and in Streptelasma Remevi, is evident. 
EXPLANATION OF PLATE VII. 
Fig. 1. A transverse section of Streptelasma Remeri, Duncan, made close 
below the calice; f denotes the position of the vertical pair of coste ; 
o of the costz of the opposite side; x the position where the costz 
change their direction (magnified). 
. The small septa which sometimes bound the fossula in transverse section, 
showing their relation to the coste. There are three coste and 
two septa, and the cost to the right are the vertical pair. one being 
without a septum and corresponding to the fossula (magnified). 
3. Two smaller septa pounding the fossula and corresponding to the ver- 
tical pair of coste (magnified). 
4. Corallum slightly magnified, showing the calice, septa, and the coste ; 
note the vertical pair and the others on either side and their direc- 
tion. 
5. The costee (magnified) ; the vertical pair are seen, and the others joining 
them at different angles. 
6. Side view of a corallum (magnified); fis at the position of the vertical 
pair, 2 is where the costz change their direction. 
7. The two central septa relate to the vertical pair of cost and arein a 
fossula which is bounded by the two larger septa; a rudimentary 
septum has appeared (magnified). 
bo 
oe 
