VERMETID^. 227 



irregularly twisted, carinated. Operculum large, smooth, circu- 

 lar, concave ; the scar of attachment central, rugose. 23 sp. 

 World-wide. M. Rougemont has obserA'ed at Naples that the 

 S. maximum (Ixvii, 74) emits from its mouth a thin veil-like 

 plaited substance, which entangles small natatory animals, and 

 is subsequently withdrawn. 



VERMETUS, Adanson. (Macrophragma, Carp. Aletes, Carp.) 

 Shell mostly spirally twisted, affixed, usually decussated, colu- 

 mella folded. Opercukim thin, concave, scarcely spiral. The 

 Yermetus of most authors is the Vermiculus of Lister. 27 sp. 

 Widely diffused. V. carinatus, Quoy (Ixvii, 75). 



PETALOCONCHUS, Lea. An American tertiary fossil. Shell with 

 two internal ridges running spirall}^ along the columella, becoming 

 obsolete near the apex and aperture. V. sculpturatus, Lea 

 (Ixvii, 76). 



THYLACODES, Guettard. (Serpulorbis, Sassi. Lementina, Gray. 

 Hatina, Gray. Cellularia, Schmidt. Cladopoma, Graj-. Tetra- 

 nemia, Morch.) Shell tubular, irregularly twisted, adherent, 

 aperture rounded, columella not plicate. No operculum, or 

 minute when present. The animal has a truncated foot, pro- 

 duced in front into tentacular processes. Many living and 

 several tertiary species ; and one cret. ; India. T. areno.ria, Quoy 

 (Ixvii, 77). 



BivoNiA, Gray. Shell affixed, mostly spiral, aperture contracted, 

 circular, with spiral, interruptedly nodulose lirse, and a median 

 elevated line ; columella smooth. Operculum small, rudimentary. 

 Animal with cylindrical tentacles, pedal filaments subulate or 

 setaceous. 7 sp. B. triquetra^ Bivona (Ixvii. 80). When the shells 

 are not perfect with the margin of the aperture, they are very 

 difficult to distinguish from Spiroglyphus. 



SPIROGLYPHUS, Daudin. Animal forming a groove on the 

 surface of shells or stones, covering it over with shelly matter, 

 and forming -a tubular case. Many zoologists consider the 

 Spirogl^qDhus to be an annulose animal allied to Serpula, but of 

 this there is no positive proof. The young animal, when first 

 hatched, is covered with an ovate, regular shell, consisting of a 

 whorl and a half; it soon attaches itself to the surface of some 

 stone or other shell, in which it forms a canal, at first shallow, 

 but afterwards deeper. S. spirorbis^ Dillw. (Ixvii, 78). 



SiLIQUARTA, Brug. 



Etym. — Siliqua, a pod. Syn. — Tenagodus, Guettard. 



Distr.-^lb sp. Mediterranean, Australia. Fossil, 20 sp. Ter- 

 tiar3^ The typical species, as well as several others, occur 

 imbedded in sponges. S. anguina, Linn. (Ixvii, 79). 



Shell tubular ; spiral at first, afterwards irregular ; tube with 

 a continuous longitudinal slit. Operculum spiral, like that of 



