210 



NATURAL HISTORY. 



numerous tuberculated whorls, the aperture narrow, but the outer lip greatly expanded, lobed, and 

 digitated ; the operculum is pointed and lamellated. The muzzle of the animal is short and broad ; 

 the tentacles are cylindrical ; the eyes are on prominences near their outer bases ; the foot is short, 

 rounded in front, pointed behind. Three species are described living at twenty to one 

 hundred fathoms, in Labrador, Norway, Britain, the Mediterranean, &c. 



Struthiolaria* is a turreted shell with angular whorls. Its aperture is truncated in 

 front ; the columella is very oblique ; the outer lip is prominent, thickened ; inner lip 

 callous, expanded ; operculum claw-shaped. Five species occur in Australia and New 

 Zealand. 



FAMILY XIV. TUREITELLID^E. 



The shell in this family is tubular or spiral, the upper part being partitioned off. 

 The aperture of the shell is simple ; the operculum horny, many-whorled. The animal 

 has a short muzzle, eyes on head at the outer bases of the tentacles, mantle fringed, foot 

 short, tongiie armed. This is a strictly marine group, the species ranging from low -water- 

 mark to a depth of one hundred fathoms. Their geographical distribution extends over 

 most of the countries of the globe, one species being an inhabitant of the British seas. 

 They are commonly called " Screw-shells," from their peculiar form. 



In the genus l\irritella (" Tower-shells"), the shell is turreted, many-whorled, spirally 

 striated, the aperture round, margin thin. The shells of this genus are spotted and 

 variegated, generally with red and brown. The species inhabit all parts of the world, 

 , being most numerous in tropical countries. The writer has taken the Tiirritdla 



PUKRITEIjLA * 



TEREBEL- coTfimunis by the dredge-full off the Bay of Malaga (Mediterranean), showing that 

 LATA. they are gregarious in their habits in soft mud. Many examples were dredged 

 showing the whorls disconnected, as in Vermetus. Fifty species are described of world-wide 

 distribution. 



When young, the shell of the genus Caecum is discoidal ; when adult, it becomes decollated, 

 and appears to be simply tubular, cylindrical, with a round entire aperture, the apex being closed by 

 a mammillated septum, marking the point where the original spire has been cast off. This curious 

 little genus has puzzled many zoologists, having been referred to the Pteropods, to the Orthoceratites, <kc. 

 Two British species have been met with living in about ten fathoms water. 



In the genus Vermetus, or the "Worm-shell," the shell is tubular and attached, but when 

 young it is regularly spiral, but always disunited and irregular in its adult growth. The tube 

 is repeatedly partitioned off, the aperture is round, the operculum circular and con Cave externally. 

 The animal has a rudimentary cylindrical foot, being unable to crawl or 

 glide, as the shells are fixed together in clusters. Vermetus is found on 

 the coasts of Portugal, the Mediterranean, Africa, and India. 



The genus Siliquaria has a tubular cylindrical shell, irregularly 

 twisted ; its apex is spiral, the aperture is circular. In Siliquaria 

 the notch for the siphon remains unclosed, so that as the shell 

 grows it prolongs the fissure through the whole length of its tube. 

 This genus was formerly regarded as an Annelid, but its molluscous 

 nature was demonstrated by M. Audouin. The typical species is found 

 in the Mediterranean, living embedded in sponges with silicious spicules. 

 Eight species are recorded. 



VERMETUS LUMBKICALIS. 

 (A) Young Shfll : (B) Adult Shells. 



FAMILY XV. MELANIADJE. 



The shells of this family are spiral, turreted, covered with a thick 

 dark-coloured epidermis aperture often channelled, or notched in front ; 

 outer lip simple ; operculum horny, spiral. The spire is often very much eroded. The animal has a 

 broad, non-retractile muzzle ; the tentacles are wide apart; eye stalks united to bases of tentacles ; foot 

 broad and short, angular in front ; mantle-margin fringed ; tongue long and linear. These animals are 

 mostly viviparous, and all fluviatile, being inhabitants of fresh-water lakes and rivers throughout the 



* From Struthio, an ostrich, from the aperture being fancifully supposed to resemble the foot of that bird. 



