848 PELECYPODA. [ F ilibranchia. 



Sect. 1. BARBATIA, s. str. 

 ]. Area decussata, Sowerby, 1833. Plate 56, figs. 2, 2a. 



Byssoarca decussata, Sow., P.Z.S., 1833, 18. Area decussata, Sow., Conch. 

 Icon., ii, pi. 12, f. 81 ; Hutton, P.L.S. N.S.W., ix, 528. Barbatia decus- 

 sata, Sow. : Hutton, J. de Conch., 1878, 53 ; M.N.Z.M., 162 ; Index, 94. 

 B. sinuata, Lamarck : Hutton, C.M.M., 79 ; not of Lamarck. 



Shell oval-elongate, equivalve, inequilateral, the anterior part 

 shorter, radiately ribbed and decussated by fine concentric lines, 

 white to brown, pilose. Beaks prominent, distant, directed forward, 

 keeled posteriorly. Anterior end rather short, regularly rounded ; 

 posterior end produced, sloping and usually sharply rounded towards 

 the basal margin, which is generally sinuate and the valves gaping. 

 Area straight, broadly triangularly grooved, not very broad. Sculp- 

 ture consisting of very numerous, unequal and close radiate ribs, 

 cut up into oblong nodules by concentric fine grooves. Epidermis 

 brown, horny, produced into rather long hair-like processes arising 

 from the interstices between the riblets ; the epidermis is mostlv 

 retained only near the margins of the valves. Colour white to light 

 brown. Interior white, sometimes with a few brownish streaks and 

 spots at the posterior end, polished outside the pallial line ; inside 

 it very finely radially striated. Margins sharp, crenulate. Hinge- 

 plate very narrow in the middle, but broadening distally. Teeth nume- 

 rous, small, vertical, and close together under and some distance be- 

 hind the umbones ; oblique, larger, and more distant towards the ends ; 

 the outer teeth are triangularly elevated, and have a denticulate 

 edge ; sometimes the anterior outer teeth are slightly V-shaped. 

 Ligament external. Adductor-scars subequal. Pallial line simple. 



Length, 58 mm. ; height, 30 mm. ; diameter, 24 mm. 



Type in the British Museum. 



Hab. Throughout New Zealand, but not common. Bay of 

 Islands ; Hauraki Gulf ; Queen Charlotte Sound, in 16 fathoms 

 (Captain Bollons) ; Chatham Islands. 



The species has a wide range of distribution. Von Martens (J.L.S., 

 Zool., xxi, 207) mentions the following localities : Mergui Archipelago, 

 Red Sea, Mauritius, Ceylon, Salang, Singapore, Celebes, Philippines, 

 New Zealand, Viti, and Paumotu Islands. 



Remarks. The byssus forms a solid laterally compressed horny 

 mass. The shell is very variable in outline, according to the indivi- 

 dual position. The byssus is attached to stones, but the animals 

 burrow in old corals in the Mergui Archipelago, &c. 



Maori Name. Turoro (fide Captain Bollons). 



Fossil in the Oligocene, Miocene, and Pliocene. 



Sect. 2. ACAR, Gray, 1847. 



+ Daphnoderma, Morch, 1853 + Fossularca, Cossmann, 1887. Type: Area 

 donaciformis, Reeve. 



Shell with the valves cancellately ribbed or costated ; hinder slope 

 subcarinate ; ligamental area narrow, leaving the anterior part of 



