OF CONCHOLOGY. 
33 
broad emarginated cusp nearly twice as long as thè base. The 
laterals grow broader and shorter toward thè edge. The outer 
thirteen laterals are tridentate. The inner laterals from thè 
eleventh to fifteenth are bidentate. The formula is 30T-30 or 
15’15'1‘15‘15. There are about two hundred rows in all. 
The following species belong to thè second section : 
SlPHONARIA THERSITES, Cpr., Annals and Mag. Nat. Hist., 
1864, xiv, p. 425. 
Cpr. (MSS.) Suppl. Rep. to thè Brit. As., 1863, pp. 627 
and 676. Stearns, shells of Alaska, Pr. Cai. Ac. Sci. 
Voi. Ili, p. 334. 
Testa parva, tenui, haud elevata, valde inequilaterali, derise 
nigro-castanea, Isevi seu interdura costulis paucis, obtusis, obso- 
letis, radiatim vix ornata ; epidermide laevi, tenui, fugaci ; costa 
pulmonali intus et extus valde conspicua, tumente ; vertice 
obtuso, plerumque ad quadrantem, interdum ad trientem totius 
longitudinis sito ; intus intense nigro-fusco, margine acuto. Lon. 
•46, Lat. ‘33, Alt. -17 in. 
Hah. Neeah Bay ; Sitka ; Vancouver’s Island ; Fort Simpson ; 
N. W. C. Am. 
The external appearance of thè animai is very plain. The 
mantle edge, sides of thè foot, and head are smooth and even. 
The lobe is stout and short. The head is small, and thè eyes 
could not be found with a high power. The soft parts are en- 
tirely contained within thè shell. The color in spirits was a 
dusky slate-color. 
The jaw is simple, arcuated and rounded at thè ends. The 
rhachidian tooth is slender with a simple pointed cusp. 
The inner nine laterals are provided with an oblique, equi- 
bidentate cusp. The tenth, eleventh and twelfth are tridentate. 
The remainder are much broader and shorter, tridentate ; thè 
centrai point more prominent than thè others, and, in thè thir- 
teenth, fourteenth and fifteenth slightly emarginate at thè tip. 
The cusps grow less conspicuous toward thè outer edge, and in 
thè outer three teeth are hardly perceptible. The formula is, 
22-1-22, or 7-3-3-9-1-9-3-3-7. 
This species having been obtained in lat. 57° N., is probably 
thè most northern representative of thè genus. 
SlPHONARIA Tristensis, Sby. 
S. Tristensis, Sby., Genera of Shells, fig. 3. Rve. Mon. Si- 
phonaria, PI. V, fig. 23a, b. 
Patella Tristensis, Leach, teste Rve. 
Siphonaria Lessoni, Blainv., teste Rve. 
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