2S0 Intelliiieiice and Miscellaneous Articles, 



'to 



Mr. Owen read a " Description of a recent Clavagella," founded on 

 the examination of an individual brought home by Mr. Cuming and 

 imbedded in siliceous grit. The portion of rock contained the whole 

 of the expanded cavity excavated for the abode of the animal, to- 

 gether with the fixed valve of its shell and about an inch of its cal- 

 careous tube : the loose smaller valve was detached from the soft 

 parts. Mr. Owen describes in detail the fixed valve, which cor- 

 responds to the left side of the animal's body ; the attachment to it 

 of the adductor muscles, two in number ; its passage into the cal- 

 careous tube by a continuance of the shelly substance ; the tube it- 

 self, which communicates with the posterior part of the chamber 

 next the side which corresponds with the ventral surface of the ani- 

 mal ; and the free valve. He regards it as probable that the animal 

 of this species, having penetrated into the rock for a certain distance, 

 then becomes stationary, and limits its operations to enlarging its 

 chamber to the extent required for the development of its ovary : 

 this enlargement takes place in the dorsal, dextral, and anterior 

 directions. 



The soft parts of Clavagella form an irregularly quadrate mass, 

 convex anteriorly, rather flattened at the sides, and slightly naiTow- 

 ing towards the posterior end, from which the smooth rounded si- 

 phon is continued. This contains the anal and branchial canals, 

 which are separated by a strong muscular septum, but do not pro- 

 ject as distinct tubes : in this respect Clavagella agrees with Gastro- 

 chccna and Aspergillum. The mantle is a closed sac, having only an 

 opening for the passage of the siphon and a small slit at the opposite 

 end for the passage of a rudimentary foot : the use of this slit in 

 Clavagella is obviously different from that assigned by M. Riippell 

 to the corresponding structure in Aspergillum. 



Mr. Owen describes the mantle and its structure ; the siphon ; 

 and the thick mass of muscular fibres at the anterior part of the 

 mantle, which forms probably one of the principal instruments in the 

 work of excavation : he also notices the great development, as com- 

 pared with the size of the animal, of the adductor muscles. He 

 then proceeds to the viscera, which generally agree with the typical 

 structure in other Bivalves. The digestive system, which accords 

 with that which is usual in Acephalous Mollusca, is described; as 

 are also the respiratory and circulating systems, the principal ner- 

 vous ganglia, and the ovary. 



The paper was accompanied by drawings illustrative of the several 

 structures described in it. 



The specimen described belongs to the species termed by Mr. 

 Broderip Clavagella lata. 



XXXIX. Intelligence and Miscellaneous Articles, 



MR. STURGEON ON AN AURORA BOREALIS SEEN AT WOOLWICH, 

 ON DECEMBER 22, 1834. 



A BEAUTIFUL Aurora Borealis was seen from this place last 

 night. I was on Woolwich Common when I first saw it, then ex- 



