609 



PYLORIDIA. 



PYRAMIDELLID^E. 



510 



it again to the surface by means of the extension and contraction of 

 its great muscular foot, which is situated at that part of the shell 

 which is lowest. Although with difficulty obtained by digging, they 

 are easily induced to come forth from their hiding places by putting 

 a little salt over their holes. They may then be easily captured. 

 Some of the species make an excellent soup. 



They are found in the seas of the whole world. There are 25 

 recent species. 



Soltn Legvmen. Shell and soft parti. 



M. De Blainville thus divides the genus : 



A . Species somewhat curved longitudinally ; umbo not terminal. 

 Ex. Solen cultellut. 



B. Species straight, or hardly curved ; umbo terminal. 

 Ex. S. Vagina. 



The British species of Solen recorded by Messrs. Forbes and Hanley 

 are S. Entii, S. marginatut, S. pellucidiu, and S. tiliqua. 



Shell of Solen Entit. 

 a, External view or valves closed ; b, internal view of valve. 



Solemya. Animal oval, transverse ; lobes of the mantle united for 

 their posterior half, terminated by two short and unequal siphons ; 

 foot proboscidiform, truncated anteriorly by a disc, or kind of sucker, 

 the borders of which are fringed ; a single bronchia on each side in 

 form of a plumule, the barbs of which are isolated up to the base ; 

 anus terminal, not floating. (Deshayes.) Shell very delicate, fragile, 

 compressed, elongated, rounded at its extremities ; the borders straight 

 and parallel, gaping a little backwards, regular, equivalve, very inequi- 

 lateral, covered with a shining epidermis, which invests it on all sides, 

 except in front and behind ; anterior side much longer than the 

 posterior; am bones but little distinct; hinge composed of a cardinal, 

 dilated, compressed tooth, which is very oblique, a little curved above, 

 serving for the insertion of the ligament in each valve; ligament 

 almost entirely posterior; muscular impressions small, rounded, 

 distant ; some traces of a pallial impression. (Rang.) 



Sands are the localities in which the genus has been found. 



Panopaa. Shell thick, solid, convex, oblique, elongated, gaping at 

 both extremities, equivalve, inequilateral, rather irregular ; umbones 

 well marked, contiguous, rather curved forward, and more approxi- 

 mated to the anterior than the posterior part ; hinge presenting a 

 conical tooth in each valve in front of a fosset, and of a thick callosity, 

 not projecting outwards, and but little elongated, on which is inserted 

 the external, posterior, and convex ligament ; muscular impressions 

 irregularly oval, the anterior the longest, both united by a pallial 

 impression, which is wide, parallel to the border of the shell, and 

 rather deeply excavated backwards. (Bang.) 



P. Aldrovandi is noted as both living and fossil (tertiary). Six 

 recent and 140 fossil species are the numbers stated by Woodward 

 in his ' Treatise on Shells.' 



The species of Panoprta hnve been found in sands and shallow 

 water. 



Glycmeris, Animal elongated, thick, cylindraceous, having the lobes 

 of the mantle very thick, open only at the anterior extremity for the 

 passage of a small cylindrical foot, and terminated posteriorly by two 

 siphons, united into a single cylindrical very fleshy mass, and never 

 capable of entering the shell ; mouth moderate, oval, accompanied on 

 each side by two large equal triangular palps, joined by their base to 

 the anterior adductor muscle. Branchife long and thick, two on each 

 side nearly equal. (Deshayes, after Audouin.) Shell with a strong 

 epidermis, elongated, rounded, gaping at both extremities, rather 

 irregular, equivalve, very inequilateral ; umbonss projecting but little, 

 skinned (e'eorche's) ; hingo toothless, presenting only a thick and but 

 little elongated callosity; external ligament supported by nymphs 

 projecting outwards; muscular impressions distinct and very distant; 

 pallial impression well marked, not excavated poateriorly; valves 

 thickened by callosities in the interior. (Rang.) 



There is but one species, which is found on sands at moderate 

 depths. 



Saxicava. [LITHOPHAGID.!!.] 



Byssomya. [BYSSOMYA.] 



Rhomboides. Animal. Body rhomboidal, elongated, rather com- 

 pressed, with two distinct tubes backwards ; a rather wide slit at the 

 anterior and inferior part of the mantle for the exit of a small conical 

 foot, with a byssus the filaments of which are enlarged at the 

 extremity. Shell rhomboidal, rather irregular, striated longitudinally, 

 very inequilateral ; umbones very distinct and very antero-dorsal ; 

 hinge formed by two small cardinal teeth ; ligament external, posterior,, 

 rather projecting ; two rounded muscular impressions. 



Ex. Rhomboides rugotus. 



Hialetta, Animal unknown. Shell delicate, elongated, sub-rhom- 

 boidal, equivalve, very inequilateral, gaping at its inferior border and 

 posterior extremity ; umbo very anterior and curved forwards ; hinge 

 dorsal, formed of a single tooth in one valve corresponding with a 

 notch on the opposite valve, or of a small tooth with a cardinal fosset 

 on each valve ; ligament probably external and dorsal ; muscular and 

 pallial impressions unknown. (De Blainville.) 



M. De Blainville divides the genus into the following sections: 



A. SpecSes with a tooth in one valve only. 

 Ex. Hiatella biaperta. 



B. Species with a small tooth on each valve. Genus Biapholius, 



Leach. 



Ex. Hiatella Arctica (My a Arctica, Oth. ; Fabr.) 

 Gaitrochoena. [GASTROCHOSNA.] 

 Clavagella. [CLAVAGELLA.] 

 Aspergillum. [AspEROiLtr/s; TOBICOLID.S.] 

 PYLORUS. [DIGESTION; STOMACH.] 



PYRALLOLITE, a Mineral occurring crystallised and massive. 

 Primary form, according to Levy, an oblique-angled parallelepiped. 

 Cleavage parallel to the two lateral faces of the primary form, and to 

 one of the diagonal planes. Fracture earthy. Hardness, scratches 

 carbonate of lime, and is scratched by felspar. Colour white and 

 greenish ; transparent on the edges ; lustre resinous. Specific gravity 

 2-55 to 2-60. 



Before the blow-pipe it becomes at first black, and afterwards white ; 

 swells and fuses on the edges into a glass, and with borax gives a 

 transparent glass. 



A massive variety, yellowish, in small laminar masses, with whi*.e 

 carbonate of lime, red phosphate of lime, and green pyroxene. It 

 occurs at Storgard, Pargas, Finland. 



Its analysis by M. Nordenskiiild gives 



Silica 56-62 



Magnesia 23'38 



Alumina 5'38 



Lime ... .... 5'58 



Oxide of Iron . . . 0.99 



Oxide of Manganese 0-99 



Water 3'58 



96-52 



PYRAMIDELLID^E, a family of Gasteropodous Mollusca. The 

 shell is spiral, turreted ; the nucleus minute, sinistral ; aperture 

 small; columella sometimes with one or more prominent plaits. 

 Operculum horny, imbricated, nucleus internal. The animal has 

 broad ear shaped tentacles, often connate ; eyes behind their tentacles, 

 at their bases ; proboscis retractile ; foot truncated in front ; tongue 

 unarmed. The species of this genus are all marine. Messrs. Forbes 

 and Hanley speak of this family as presenting " subjects of much 

 interest to the student of extinct Mollusca, numerous forms having 

 all the aspect of being members of this family occurring among the 

 fossils of even the oldest stratified rocks. Many of them are gigantic 

 compared with existing species, and the group, as a whole, may 

 be regarded rather as appertaining to past ages than to the present 

 epoch." 



The genera embraced in this order nre Pyramidella, Oidoilomia, 

 Aclis, Stylifer, Chemnitzia, Eulima, EulimeUa, Stylina, Loxonema, 

 Macrocheilus, Truncatella, Otina. 



Pyramidella has 11 recent and 12 fossil species. The recent 

 species are found in the West Indies, Mauritius, and Australia. The 

 fossil in the chalk. 



