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XXIX. On the Anatomy of Clavagella, Lam. By Ricuarp Owen, Esq., F.R.S. & Z.8., 
Assistant Conservator of the Museum of the Royal College of Surgeons in London. 
Communicated September 23, 1834. 
THE specimen of Clavagella which forms the subject of the following description was 
dredged up by Mr. Cuming, and belongs to the species which my friend Mr. Broderip 
has characterized and named Clavagella lata. 
The soft parts of this specimen were placed in spirit by Mr. Cuming soon after it 
was captured, and were thus transmitted in good state for examination to this country. 
They differ considerably from the form which the soft parts commonly assume in other 
Bivalves, being, as it were, aggregated into an irregular quadrate, or transversely ob- 
long mass, convex anteriorly, compressed laterally, and contracting towards the poste- 
rior end of the body, which is formed by the smooth rounded siphon containing the 
anal and branchial canals. The exterior layer of the mantle, which envelopes the soft 
parts, is a thin lacerable membrane, with two openings, one anterior, contracted to a 
very small size, for the passage of the rudimentary foot, the other posterior, corre- 
sponding to the respiratory and excremental outlets. 
When the soft parts are replaced in their natural position in the clavate chamber’, 
and exposed by the removal of the outer layer of the mantle, they present the appear- 
ance delineated in Plate XXX. Fig. 11. Much less of the organization of the animal 
is by this means brought into view than in most other Bivalves, in consequence of the 
great development of the muscular margin of the mantle. The true foot is wholly con- 
cealed, and only the extremities of the labial appendages and a small part of the right 
gill are seen protruding through the interval between the anterior muscles of the 
mantle and those which go to form the siphons: a small part of the ovary may be seen 
between the anterior and posterior adductor muscles. 
The relative position of the animal of Clavagella to the rocky chamber which it in- 
habits is as follows. The mouth is turned towards the closed end of the chamber 
marked a, which is consequently the anterior part. The heart and rectum are nearest 
the side where the valves are connected by the ligament b, or the dorsal part: 
the visceral mass projects towards the opposite or ventral side c, while the siphon ex- 
tends into the commencement of the calcareous tube d, which leads out of the anal or 
posterior part of the chamber. The fixed valve, which covers the rough surface of the 
porous rock or coral, like the tiling of a chamber floor, and affords a smooth polished 
surface for the support and attachment of the animal, is the left valve: the right valve 
1 Plate xxx. Fig. 8, 
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