24 
XArXlLOIDEA. 
b. Annidated Species. 
Trochoceras STibcostatum, Angelin, sp. 
1880. Discoceras subcost atmn, Angelin, in Angelin A Lindstrcim’s 
Fragmenta Silurica, p. 10, tab. ix. ff. 13, 14, tab. xi. fE. 5-8. 
Sj). Char. The shell consists of about three whorls, in which, 
judging from Angelin’s figure, there is very little asymmetr}*. The 
last whorl leaves the coiled portion and is prolonged into a free 
curved piece for a distance of half the last volution, and is there 
broken off, so that the aperture is not seen. The section is subquad- 
rate, the ventral side being considerably flattened, as represented in 
Angelin’s figure. The shell increases its diameter about 2| times 
in the course of a volution. The septa are very close together, 
their distance being everywhere about the same, viz. from 1 to 14 
lines ; they are moderately concave. The siphuncle is situated 
between the centre and the ventral or convex border. The surface 
of the test is ornamented with obscure transverse annulations and 
rather coarse lines parallel to them, which form a conspicuous 
backwardly directed sinus on the periphery. 
Bemarl's. The above description is taken partly from Angelin’s, 
as the specimen in the British Museum is not sufficiently perfect to 
furnish all the characters of the species, the operations of the lapi- 
dary, before it came into the possession of the Museum, having 
reduced it to a very thin slab, which, however, shows the outline 
of the whorls, and the commencement of the free portion, as well 
as the septa and siphuncle. 
This species is distinguished from T. lamellosnm, Hisinger, sj)., 
by its ornaments and by its narrower and less rapidly increasing 
whorls. 
Horizon. Or#7mc€ras-Limestone ( = Arenig). 
Locality. KinnekuUe Hill (Westrogothia), Sweden. 
Eepresented in the Collection by a single example presented by 
J. E. Lee, Esq., E.S.A., F.G.S. 
Trochoceras regulare, Blake. 
1882. Trochoceras reguJare, Blake, British Foss. Ceph. pt. i. p. 221, 
pi. xxix. f. 7. 
Sp. Char. The shell increases its diameter about twice in the 
last whorl. “ The section is a rather flattened oblong, rounded at 
the edges. The whorls slightly overlap, and there is decided asym- 
metry. The ornaments consist of very clean and separate back- 
ward-curving ribs, 22 per whorl, which stand out from the flat 
