868 PELECYPODA. [l-'ilibranchia. 



straight to its middle, thence descending in a regular curve. Posterior 

 end compressed, broadly rounded, the basal margin slightly concave 

 at the middle. Sculpture consisting of concentric growth-lines. Epi- 

 dermis coriaceous, slightly shining, brown. Colour brownish-black. 

 Interior bluish-white, purple round the dorsal and posterior margins. 

 Margins smooth, sharp. Hinge-line narrow, smooth. Ligament long 

 and narrow, mostly internal. Adductor-scars distinct, but hardly im- 

 pressed. Pallial line simple. 



Diameter Ant.-post., 25 mm. ; dorso- ventral. 13 mm. : thickness, 

 12 mm. 



Type in the Dominion Museum, Wellington. 



Hab. In brackish water throughout New Zealand. The type is 

 from the Great Lagoon, Chatham Islands. 



Remarks. This species is nearly allied to M. ater, but the beaks 

 are situate farther back, the shell is generally less curved, and the 

 colour is not so intensely black, more brownish. It is, as a rule, much 

 more winged posteriorly. 



Genus 3. MODIOLARIA, Beck, 1840. 



Modiolaria, Beck, in E. Robert, Zool. Voy. " Recherche " en Isl. et en Gronl.. 

 pi. 17, f. 1-4, 1840. Type : Mytilus discors, L. Modiolaria, Loven, 

 Ind. Moll. Scand., 1846,' 33. Lanistes, Swainson, Malac., 1840, 385 ; 

 not of Montfort, 1810. Lanistina, Gray, P.Z.S., 1847, 199. 



Animal having the mantle widely open ; siphons elongated, the 

 branchial one being usually shorter and not closed along its lowei 

 side, but merely with apposited free edges. Foot long and tapering 

 to a point, vermiform, grooved, and with a byssiferous gland. 



Shell rhomboidal, inflated, generally with 3 areas, the two at the 

 ends radially sculptured ; sometimes the shell is radiately ribbed 

 throughout, or it may be smooth ; beaks incurved, placed near the 

 anterior end. Ligament linear, marginal. Hinge-plate smooth or 

 crenate. 



Distribution. All seas ; several species in cold seas. 



Fossil. Secondary and Tertiary. 



KEY TO SPECIES. 



A. Shell small, elongately ovate, with fine radial riblets, strongly 



sericate posteriorly . . . . . . barbata. 



B. Shell larger, ovate and ventricose, with stout radial ribs, not sericate impacta. 



1. Modiolaria barbata, Reeve, 1858. Plate 63, fig. 3. 



Lithodomus barbatus, Reeve, Conch. Icon., x, pi. 5, f. 27. L. laniger, Reeve, 

 i.e., pi. 5, f. 30. Modiolaria barbata, Reeve: Angas, P.Z.S., 1867, 911, 

 pi. 44, f. 12. Crenella barbata, Reeve : Angas, I.e., 1878, 871. Modio- 

 laria lanigera, Reeve : E. A. Smith, Chall. Rep., xiii, 278. M. barbata, 

 Reeve, Index, 94 ; Pritchard and Gatliff, P.R.S. Vic., xvii (n.s.), 254. 



Shell small, thin, transversely ovate, hirsute posteriorly, thin, 

 light yellow. Beaks approximate, near the anterior end, tumid, angled, 



