1020 PELECYPODA. [Eulamellibranchia. 



the posterior auricle is not very large, about the size of the front triangle 

 or smaller, convex, dorsally somewhat excavated. Front dorsal area 

 on each valve semicircular, limited by a sharp carina, excavated, but 

 with a central elevation which is rugosely concentrically grooved. 

 Posterior dorsal area long, narrow, excavated and inclined, bounded 

 by a sharp ridge. Sculpture : The front triangular area is concen- 

 trically traversed by elevated close-set striae, which diverge from the 

 anterior dorsal edge ; to these succeed another series of much finer 

 and denser lines, crossed by microscopic fine transverse striae, pro- 

 ducing a subgranular decussation ; these striae, uninterrupted by 

 either linear callosity or impressed striae, unite almost at right angles 

 with the striae of the anterior area, and occupy a more or less narrow 

 triangular strip of surface, extending from the beaks to the ventral 

 tubercle ; posteriorly they are limited by a linear groove, beyond 

 which more distant concentric lines are visible, which very quickly 

 become obsolete, leaving the hinder side almost smooth ; the auricle 

 has fine confluent verrucose granules. Epidermis thin, olivaceous. 

 Colour olivaceous to very light brown ; chestnut behind the line 

 descending from the beaks to the anterior part of the base ; white 

 underneath the epidermis. Internally there is a kind of prolongation 

 of the beaks, in the shape of a protuberant callosity, which leans 

 towards the interior, and does not project above the dorsal line ; this 

 is terminated in the right valve by a narrow shelf-like rim, and in the 

 left by a projecting and recurved tubercular lamina, which juts out 

 rather obliquely. The apophysis is moderately oblique, and presents 

 its broader side to the inner disc ; it is very thin, and rather wide, 

 swelling out a little at its anterior edge. The tubercle which terminates 

 the ventral edge is very solid and not broad, prolonged upwards into a 

 short sharp ridge, continuous with a faint sulcus corresponding with 

 the line on the surface of the body limiting the finely striated anterior 

 area ; this part of the shell has a much thicker callosity than the 

 anterior part. Margins : The anterior margins are smooth and sharp, 

 the lower one microscopically sharply denticulate ; posterior margins 

 smooth, blunt. Pallets penniform, somewhat spoon-shaped, convex 

 on one side and concave on the other ; a rib-like elevation running 

 down the centre of the latter projects beyond it, and forms a slender, 

 cylindrical, and sometimes flexuous handle. Testaceous tube with thin 

 walls, semiconcamerated at its narrower end ; the central opening 

 left is oval, but the tube is circular in cross-section. 



Measurement of valves from Auckland Harbour : Diameter 

 Ant.-post., 10 mm. ; dorso-ventral, 10 mm. : transverse diameter of 

 one valve, 4 mm. 



Type, of T. antarctica in the Dominion Museum, Wellington. 

 Hob. Auckland to Dunedin (Button). 



Remarks. I have been able to collect a number of valves, pallets, 

 and tubes of this species from an old wharf-pile, Auckland Harbour, 



