125 



Turritella atkinsoni, Tenison- Woods. Var. medioangu- 

 lata, n. var. PI. xxx., figs 8 and 9. 



Shell rather thin, turriculate, of twelve whorls, including 

 a sKghtly mamillate blunt protoconch of two convex smooth 

 whorls. Suture distinct, linear. Whorls medially strongly 

 angulate and feebly carinate, sloping to both sutures, con- 

 cavely to the lower, and feebly swollen midway to the upper. 

 The first and second whorls are bicarinate, the lower carina 

 is the rather less valid and gradually decreases to an obsolete 

 spiral stria. 



In successive whorls new strise arise, so that in the pen- 

 ultimate there are three in the upper and four in the lower 

 half of the whorl, but all obsolete. The body-whorl has a 

 round cord-like carina forming the periphery at the suture, 

 beyond which the base is nearly flat, slightly concave, and 

 with numerous sublenticular spiral strise. Aperture roundly 

 hexagonal, with a wide effuse base ; outer lip thin, roundly 

 angled at its centre (the carina ceasing some distance from 

 it), with a wide deep sinus having its centre at the angula- 

 tion. Columella curved. Colour yellowish-brown, lighter 

 along the suture, the earlier whorls translucent- white, tinted 

 brownish along the angulation. 



Dim. — Length, 12*9 mm.: breadth, greatest 3'6 mm., 

 least 3 mm. 



Locality. — Type in 104 fathoms 35 miles south-west of 

 Neptune Island, with more than 80 others; in 110 fathoms 

 off Beachport, 7 fresh, 4 poor ; in 150 fathoms, 39 good : 

 in 200 fathoms, 29 large but poor, only 2 good ; in 90 fathoms 

 off Cape Jaffa, 24 good and alive, 55 small ; in 300 fathoms, 

 15 poor and small. It would seem, therefore, to favour 90 to 

 200 fathoms, and to be essentially a deep-water form. I have 

 not taken a specimen at any less depth. 



Variations. — It may reach a length of 17' 7 5 mm. and 

 have fourteen whorls. The angulation may be provided with 

 a distinct carinating cord. One of the spiral striae just behind 

 this may also become a valid cord, and together with these, in 

 other specimens, the peripheral spiral may appear just above 

 the suture, with another valid spiral close behind it. These 

 differences suggest conspecifity with T. atkinsoni, Tenison- 

 Woods, although my typical shell, and the boldest-ribbed 

 examples) of his species, are very unlike. But he described 

 his type as having "two principal keels" ; T. godeffroyana, 

 Donald, has three, and Tate says T. atkinsoni has four. The 

 two figures drawn by Tate and May in Proc. Linn. Soc, 

 New South Wales, loc. cit., show two very dissimilar forms, 



