246 
Kalkskjael. Den ydre Beklsedningsmembran overalt ru af 
fine Smaapigge. Farven ensformig livid. Laengden indtil 
Findesteder. Stat. 18, 35, 312. 
B erase rkninger. Denne anselige Form er strax kjen- 
delig fra de 2 foregaaende Arter, foruden ved sin betyde- 
lige Sterrelse, ved den overalt af fine Smaapigge ru ydre 
Bekkedningshinde og ved den sserdeles tydelige og elegante 
Scnlptur af Skallens Valvler, hvilket har givet Anledning 
til A rtsbena 1 vnelsen. 
Beskrivelse. Legemet er (se PI. XX, Fig. 5 & 6) 
forholdsvis kort og undersmtsigt, med Oapitulum betydelig 
baade lsengere og bredere end Stilken. Det har en lig- 
nende Stilling i Forhold til de Gjenstande, hvortil det er 
faestet soin hos Sc. angustum, idet Stilken ingen mmrkbar 
Boining viser. 
Oapitulum er seet fra Siden (Fig. 5) temmelig regel- 
msessigt ovalt eller elliptiskt, mere end dobbelt sda langt 
som bredt, med den ventrale Band jevnt buet og Apex 
forholdsvis kort. men skarpt tilspidset og noget opadkrummet 
samt beliggende nmsten noiagtig i Skallens Axe. Yalvlerne 
er indbyrdes meget fast forbuudne, idet de stode umiddel- 
bart op til hverandre og kun er skilte ved smale, tildels uty- 
delige Suturer. De viser alle en meget skarpt udprseget 
og elegant Sculptur, idet der foruden concentriske Vtext- 
striber findes talrige, tildels kjoltormigt fremspringende ra- 
dierende Bibber. 
Kjolen er som hos foregaaende Art ganske smaljog 
jevnt buet, uden nogen tydelig Umbo og fortssetter sig 
nedad lige til Stilkens Begyndelse. 
Torgalstykkerne er meget store, men har Aabnings- 
randen kjendelig kortere end Basalranden. 
Skjoldene er forholdsvis smale, og af en lignende 
uregelmmssig 4-sidet Form som hos do 2 foregaaende Arter; 
dog er Tergalranden her neppe lsengere. end Basalranden 
og begge betydelig kortere end Lateralranden. Det apicale 
Hjorne er ligesom hos Sc. angustum spidst udtrukket. 
De ovre Sidestykker har det dorsale mod Kjolen 
vendte Parti noget kileformigt afsmalnende og den ventrale 
Band uregelmsessigt bugtet. De viser en meget tydelig 
subcentral l mbo, hvorfra 5 mere fremspringende Kjole 
radierer. 
Af Basalstykkerne er de dorsale temmelig store og 
brede, uregelmtessig 4-sidede og viser intet Fremspring ved 
Boden; de mellemste Stykker er meget smaa og af en fra 
sannno hos de 2 foregaaende Arter vsesentlig forskjellig 
Foim. idet de er smalt triangulsere eller kileformige, med 
Spidsen vendt mod Basis ; de ventrale Stykker er mere end 
dobbelt saa. store og af 4-kautet Form. 
with large imbricate calcareous scales. Outer investing 
membrane everywhere rough, from numberless minute spike- 
lets. Colour a uniform white. Length reaching 35"””. 
Locality. — Stats. 18, 35, 312. 
Remarks. — This large and striking form can be 
at once recognized from the 2 preceding species, not only 
by its considerable size but also bv the outer investing 
membrane, rendered everywhere rough from minute spike- 
lets, and the very distinct and graceful sculpture on the 
valves of the shell, a character that suggested the specific 
designation. 
Description. — The body (see PI. XX, figs. 5. 6) 
is comparatively short and thickset, with the capituluw 
both longer and broader than the peduncle. It has a 
position in relation to the objects whereto it is attached 
similar to that in Sc. angustum , the peduncle not exhibit- 
ing any appreciable flexure. 
The capitulum, viewed from the side (fig. 5). is ap- 
proximately of a regular oval or ■ elliptic form, more than 
twice as long as broad, with the ventral margin evenly 
arched and the apex comparatively short, but acutely pointed 
and curving slightly upward, as also well-nigh coinciding 
with the axis of the shell. The valves are very firmly 
connected, coming as they do in close contact, with but 
narrow and partly indistinct separating sutures. They a 11 
exhibit a very sharply pronounced and graceful sculpture, 
a number of keel-like, radiating ribs occurring along with 
concentric striae of growth. 
The keel, as in the preceding species, is quite slender 
and evenly arched, without any distinct umbo, extending 
downward to the commencement of the peduncle. 
The tergal segments are very large, but have the 
occluding margin appreciably shorter than the basal. 
The shields are comparatively narrow, and of a similar, 
irregular-quadratic form to those in the 2 preceding spe- 
cies; the tergal margin, however, is scarcely at all longer 
than the basal, and both are much shorter than the lat- 
eral. 1 he apical corner occurs, as in Sc. angustum, acutely 
produced. 
The upper lateral segments have the dorsal part 
turned towards the keel, somewhat cuneiform-tapering, with 
the ventral margin irregularly flexuous. They exhibit a very 
distinct subcentral umbo, from which radiate 5 more pro- 
minent carinae. 
Of the basal segments, the dorsal are rather large 
and broad, irregular-quadratic, and exhibit no projection 
at the base; the median segments are very small, and of 
a form essentially different from that distinguishing the said 
parts in the 2 preceding segments, being narrow-triangular 
or cuneiform, with the point turned towards the base; the 
ventral segments are more than twice as large, and qua- 
drangular in form. 
