ASPERGILLUS! . 



Plate I. 



Genus ASPERGILLUS!, Lamarck. 



Testa valvis dnabus aqualibus minulis ovalis, sispissime pos- 

 lice ang/datis, in pariele inferiori vagina longce ferru- 

 minalis ; vagina superne pernio., interdum attenuatd, 

 Umbo simplici, interdum subrectd, Umbo suhampliter 

 bifariam ad octofariam foliaceo, inferne clavatd, disco 

 perforato plerumque tubulo-jimbriato clausd. 



Shell with two equal minute ovate valves, mostly angled 

 posteriorly, 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 

 disc. 



The Aspergillum is a siphoned bivalve, which 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 calci- 

 fying functions to the formation of a 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 en- 

 larges with the growth of the siphons for their special 

 protection ; downwards the animal closes in the sheath by 

 a disc, not only fissured and perforated, but bordered, in 

 most species, by a profusely tubuled frill. The mantle of 

 the animal, observed by Dr. Riippell, on the shores of the 

 Red Sea, changes and enlarges, and a number of tenta- 

 cles are emitted from the edge, each one corresponding 

 with a tubular perforation of the shell. Frequent distor- 

 tion is imparted to the shell, more especially to the disc 

 end of it, the seat of the mollusc, according to the cir- 

 cumstances of its place of habitation, and when affixed 

 to shell or stone the disc may be scarcely recognizable. 

 Shells with the strength of growth even of Spondylus, be- 

 come distorted by their inability to contend with the out- 

 ward 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. As- 

 pergillum vaginiferum, which sinks into sand, as may be 

 seen by the particles agglutinated to the shell, throws up 

 a bold erect sheath without let or hindrance, and when it 

 reaches the surface, the edge, as in Clavagella, becomes ele- 

 gantly furbelowed. A season of rest ensues; another ef- 

 fort is made to extend the sheath, the growth is pushed on, 

 but the calcifying energies of the mollusc either are not 

 needed, or are enfeebled. A little is added to the sheath, 

 and the edge is again furbelowed, and in some specimens 

 as many as eight times this process has been repeated. 



In adherent species, such as A. Strangei, one specimen of 

 which was found affixed to the inner cleft of a mussel- 

 hinge and the other to a stone, the disc is completely 

 smashed in, as it were, and the sheath being free, not 

 pushed through sand or any debris of shells or pebbles, is 

 smooth and tortuous, faintly coloured by an enveloping pe- 

 riostraeum. I incline to dissent from Dr. Gray's views that 

 the sheath of the adhering A. Strangei is an enlargement 

 of the primitive pair of valves, while in the non-adhering 

 species it is analogous to the tubular sheath of the Tere- 

 do. The sheath of Aspergi.il/im has, as in Teredo, a specific 

 limit and mode of growth, but whether by a stretch of phi- 

 losophical induction it be regarded as an enlargement of 

 the primitive pair of valves or not, the relation between 

 the valves and the sheath I hold to be the same, whether 

 living buried in sand or adhering in an exposed manner to 

 shell or stone. 



Dr. Gray also draws a distinction between species which 

 have a wavy depression around the pair of valves, and 

 those which have not, regarding the wavy depression as a 

 part of the valves of which only the umboes are exposed. 

 My own view is, that, at the time of the metamorphosis of 

 the mollusc, the valves are not larger in any species than 

 are defined by the smaller outline. When it is considered 

 that the valves are cast at this time, but not entirely, inas- 

 much as they are appropriated as material for a nucleus from 

 which to develope a sheath, it is only reasonable to suppose 

 that the new sheath-matter would, for a time, obtain a wavy 

 deposit corresponding with the outline of the nucleus. 



Nineteen species of Aspergillum are described in the 

 following monograph, but it is more than probable that 

 they will be reduced by further researches to about a 

 dozen. They have been named in Sir. Cuming's collec- 

 tion by Dr. Chenu of Paris, and I have preferred to give 

 them as he gave them, except in a few instances, where 

 the identity with others was too obvious to be overlooked. 

 More specimeus of the seven or eight doubtful species are 

 needed before rejecting them as synonyms, or discussing 

 their characters with anything like critical accuracy. There 

 are six well marked types of Aspergillum : — 1. A. vagini- 

 ferum [Warnea, Gray), in which the sheath is furbelowed at 

 the top, and has a well-fringed disc at the bottom, with a 

 wavv depression around the valves. 2. A. Cumingianum, 

 in which the sheath has a clumsy distorted growth peculiar 

 to the species, and is closed at the bottom by a rudely 

 convex disc, perforated by a bunch of tubes, not radiating 

 in a frill ; the formation of the sheath commences round 

 the valves in a depressed wavy manner, as in the preced- 

 ing species, and Dr. Gray places it for this reason in his 

 genus Warnea. I do not regard this wavy depression as 

 having existed whilst the mollusc was in the bivalve stage 

 of its existence, and would refer A. Cumingianu; 



June, 1860. 



