62 LECTURES ON MOLLUSCA. 



Family VERMETIDJE. (Worm-Shells.) 



On almost all shells and stones that have lain long in the sea are to 

 be found irregularly twisted shells, sometimes assuming a more or 

 less spiral form, sometimes almost straight. A large proportion of 

 these have no connection with shell-fish : being true worms, the sea 

 analogues of the earthy tribes : jointed animals with red blood and 

 symmetrical organs. When taken alive, these are recognized by the 

 beautiful bunch of feelers, bearing an operculurn (sometimes adorned 

 with stag's horn processes, and never spiral) on a fleshy cup in the 

 middle. Some of these,, as the tiny Spirorbis, so prolific on sea 

 weeds, stones, &c., in the colder seas, have pretty regularly formed 

 spiral shells. But in the tropical and warmer temperate regions, 

 many species are found, the animal of which is not indeed so beauti- 

 ful, but far more highly organized. It is indeed a true mollusk, arid 

 may be considered a degraded Turritella, adapted to a fixed life ; just 

 as Magilus is a degraded Purpura. 



In Vermetus proper, the shell begins exactly like a ridged Turritdla. 

 The animal is of course then free, and will probably be found to have 

 its foot somewhat developed. But after a season,, tiring of its too 

 great exertions, it lies down in a safe place, attaches itself to the moor- 

 ing, and continues its shell in an irregular twist. The foot then 

 becomes obsolete, or rather serves the purpose of a support for the 

 operculurn. The head has short tentacles with little eyes ; and a small 

 muzzle, often cleft into false tentacles, as in Ampullaria, Eissoella, 

 and the Slipper Limpets. The teeth have not yet been examined. 

 The gill is very long and slender ; and the mantle edge is sometimes 

 fringed. 



The shells of Sipkonium, though spiral at birth, have no Turritelloi< ! 

 portion. The operculurn is thin and concave, with very few whirls : 

 in Aletes, it is many-whirled, as in the Screw-shells, but small in pro- 

 portion. In Bivonia, the operculurn is shaped like a " wide-awake" 

 hat, so as to be drawn very tightly into the shell : the outside is ter- 

 raced, and often encrusted. In Petaloconchus, the operculurn is very 

 thin, and the middle whirls of the loose spire very curiously cut up 

 by thin spiral laminre, reminding one of Nerincea, or of a drawn out 

 Calyptrreid. These two last groups are often twisted together in 

 large masses, stretching out straight tubes at the end to get the best 

 access to the currents. The shell of Spiroglyplms is partly imbedded 

 in the living shells to which it adheres, growing in the form of Spi- 

 rorbis. In Serpulorbis and Cladopoda, there is no operculum, the 

 foot of the latter being produced like a club. The shells of Siliquaria 

 have either a slit or a necklace of holes, running along the whole 

 outer edge of the irregular spire ; corresponding with a slit in the 

 mantle to admit water to the long gills. The operculum is terraced 

 as in Torinia. The animal is said to be hermaphrodite ; another mark 

 of inferior development connecting this with the next order. 



The shells of this family cannot be certainly distinguished from 

 those of sea worms ; but can in general be recognized by their compact 

 porcellanous texture, glossy within, like an unrolled Turritella: while 

 the worms are generally of dead hue, and earthenware consistency. 



