474 
THE OEOLOOIST. 
named cliaraci or is that wliicli generally distinguishes it best from T. hastata 
and T. reMcnUtrix ; but, altiiongh this peculiar sinus is well and deeply 
marked in inauy individuals, it is at times but obscurely seen in others ; and 
this circumstance has no do\il)t tc'mpted some ])ala;()ntologists to unite both 
Sowerby's and Martin's shells undei- a single denomination. 
I am acquainted with but few Scottish specimens. It was found by Dr. 
rieming somewhere in West-Lothian; and Mr. Armstrong collected a few 
examples at West Broadstone, near Beilh, in Ayrshire. 
III. — Terebratula yesicularis. De Koninck. PI. xii., fig. 5. 
Terebratnla vesicularis, De Koninck, Animaux Fossils de la Belgique (Suppl.), 
p. 66fi, pi. Ivi., fig. 10, 1851. Dav. Mon. Carb., p. 15 ; pi. i., figs. 25, 
26, 28, 31, 32 ; pi. ii., figs. 1-8. 
Tliis small shell usually presents an ovate or pentagonal shape, is longer 
than wide, with its greatest breadth near tlie midcUc. In some adult examples, 
and m aU young individuals, tlie valves are evenly and moderately convex, but 
after a certain age a sinus with two lateral ridges is developed in the dorsal 
valve ; and at a still later period a small central elevation or rib is produced 
towards the front, forming a somewhat W-shaped frontal wave, of which the 
angles would be rounded. The ventral, or larger valve, is deeper and more 
innated tlian the opposite one ; the beak rounded and incurved ; for;imen small, 
and partly surrounded and separated from the huige-line by a small deltidium ; 
surface smooth. The internal dispositions are quite similar to those of 
T. hastata and T. sarculus. T. vesicularis is a small shell, and mtay be distin- 
guished from the last-named species by the small mesial rib in the dorsal valve. 
I am acquainted with but one or two examples which were found some- 
where in West-Lothian by the late Dr. Fleming. 
[NOTA. — The three sjieoies of Terebratula above described are all with which I am 
aciiuainted ft-om the Cai'boiiiferous rocks of Scotland. At page 17 of my " Monograph," 
published by the Palseontograjihical Society, I mentioned that Dr. Fleming' possessed a Terc- 
Ijratula ft-om West-Lothian, which I thought might be refen'ed to Terelrutuhi G-iUingeniiia ; 
but, after further examination, it has appeared to me that the specimen in question may be 
only a young shell of T, hastata.'} 
Family SpiRiFERiDiE.* 
Of the several genera and sub-genera of wliich this family is composed, 
Athjris, Retzia, Spirif'-ra, and Spinferina alone have hitherto been found re- 
presented in the Scottish carboniferous strata. All are provided with spiral 
appendages for the support of the oral arms. 
Genus Athyris, M'Coy, ISl-l. (Spirigera, d'Orbigiiy.) 
The species belonging to this genus bear so much external resemblance to 
many species of Terebratula, that they were for long referred to that genus ; 
but they are clearly distinguished by their non-perforated, or fibrous shell-struc- 
ture, as well as by their internal arrangements. 
The Carboniferous rocks of Scotland have hitherto furnished us with but 
three species, viz., A. amhigua, A. jdano-sulcata, and A. Rot/ssii. 
IV. — Athyris ambigua. Sowerby sp. PI. xii., figs. 6-9. 
Spirifera amligua, Sow. Min. Con., vol. iv., p. 105, tab. ecclxxvi., 1822; 
Athyris ambigua, Dav. Mon. Cai-b., p. 77, pi. xv., figs. 16-22, and pi. xvii., 
figs. 11-14. 
In external shape it is more or less obscurely pentagonal, and generally 
rather wider than long. The valves are moderately convex ; the dorsal one 
* At page 457 and following of the first volume of " The Geologist" the reader wiU find 
copious details and illustrations in connection with the genera and sub-gonera of which this 
famiUf is compoBCd. 
