177 



left valve being cemented to the wall of the burrow. Above is the 

 frilled extremity of the tube, the lower frill showing where the tube 

 once terminated, and the animal rested for a time. 



Genus 4. ASPERGILLUM, Lamarck. 



Animal ; elongated ; mantle closed in front except a minute slit 

 for the passage of a small conical foot ; edges of the mantle 

 furnished with numerous tentacular filaments, sometimes pro- 

 fusely so ; branchiae long and narrow, continued into the bran- 

 chial siphon. 



Shell ; with two equal, minute, ovate valves, mostly angled poste- 

 riorly, soldered into the lower wall of a long sheath ; sheath at 

 the upper part open, sometimes attenuated, with the edge simple, 

 sometimes nearly straight, with the edge rather largely two to 

 eight times furbelowed, at the lower part club-shaped, closed by 

 a perforated, generally tubularly fringed, disk. 



The Aspergillum, as is doubtless the case with the other genera of Tubi- 

 cola, ceases in an early stage of its existence to live free, and while yet no 

 more than the eighth of an inch in length, sinks into the sand or adheres 

 to shell or stone, and directs its calcifying functions to the formation of a 

 very long tubular sheath. The little valves, at this stage of the animal's 

 metamorphosis, if it may be so called, appear to be discarded, and taking 

 henceforth no part in the economy, they become soldered into the wall of 

 the sheath. Upwards the sheath enlarges with the growth of the mantle 

 and siphons for their special protection ; downwards the animal closes in 

 the sheath by a disk, not only fissured and perforated, but bordered, in 

 most species, by a profusely tubuled frill. The mantle of the animal, ob- 

 served by Dr. Ruppell, on the shores of the Red Sea, changes and enlarges, 

 and a number of tentacles are emitted from the edge, each one correspond- 

 ing with a tubular perforation of the shell. Frequent distortion is im- 

 parted to the shell, more especially to the disk end of it, according to the 

 circumstances of its place of habitation, and when affixed to shell or stone 

 the disk may be scarcely recognizable. Shells with the strength of growth 

 even of Spondylus, become distorted by their inability to contend with the 

 outward pressure of foreign bodies. Shells, therefore, of the delicate and 

 comparatively fragile growth of Aspergillum, would be liable to extreme 

 contortion ; and so it is. Aspergillum vaginiferum, which sinks into sand, 

 as may be seen by the particles agglutinated to the shell, throws up a bold 



VOL. II. 2 A 



