SYSTEMATIC I3S 



Genus Tromina Dall, 1918 

 Type (o.d.) : Fusus unicarinatus Philippi, Strait of Magellan 



This generic name was provided on the basis of a few empty shells from the Strait of Magellan in 

 20 fathoms, and although comparisons with the Neptuniidae were made by Dall (1902) he considered 

 the genus to be Trophonoid (Dall, 19026, p. 536). 



In 1925 Dall (pi. 21, fig. 7) figured the species for the first time, showing a strongly keeled shell very 

 similar to a new species from Clarence Islands, 6i° 25' 30" S, 53 46' W, which proves to be Cominellid 

 close to Pareuthria. 



These shells have a relatively large, dome-shaped protoconch with a smooth, blunt nucleus, but later 

 developing brephic axial threads and fine spiral striae. The operculum is horny, ovate and paucispiral, 

 occupying about half the area of the aperture, and the radula has a tricuspid central tooth and bicuspid 

 laterals. The radula resembles that of Pareuthria except for the form of the laterals, which have the 

 cusps set closer together, the inner one massive and incurved. A similar style of radula occurs in the 

 species Notoficula problematica n.sp., described following. 



I have included in Tromina a group of smaller Magellan species with rounded whorls and numerous 

 regular spiral cords, crossed by weak axial threads, but they lack the prominent keels of both the geno- 

 type and the Clarence Island tricarinata. The protoconch, operculum and radula, however, are similar 

 to those features in the typical species, Fig. N, 103, 126, p. 196. 



Tromina tricarinata n.sp., PI. X, figs. 64, 65 



Shell small, dull white, biconic, the body-whorl with three strong spiral keels. Whorls five, including 

 a large, blunt, dome-shaped protoconch of two whorls, the first smooth and almost flat-topped, the 

 second with numerous fine crisp axial threads and dense microscopic spiral striae. First post-nuclear 

 whorls with a prominent, bluntly rounded, median keel, the penultimate with a. second keel emergent 

 at the lower suture and the body-whorl with three keels. Outline of shell strongly concave on the 

 shoulder, between the keels and below the lowest keel on the base. Surface delicately reticulated by 

 dense axial and spiral threads. The spirals, which are slightly stronger than the axials, number about 

 fourteen on the shoulder of the body-whorl, five on the rounded keels, nine to eleven between the keels 

 and about thirty below the lowest keel. Spire less than height of aperture plus canal. Aperture produced 

 below into a short open spout-like canal. Outer lip thin, columella strongly incurved above and spirally 

 flexed below. Operculum small, occupying about half the area of the aperture, ovate, thin, horny and 

 paucispiral, the nucleus subterminal and on the inner side. 



Height 13-5 mm.; diameter 8-5 mm. 



Type locality. St. 170. Off Cape Bowles, Clarence Is., 61 ° 25' 30" S, 53 46' W, 23 Nov. 1927, 

 342 m. 



Dentition. Fig. L, 71, p. 194. 



Tromina fenestrata n.sp., PI. VI, fig. 14 



Shell small, white, squat, sculptured with numerous sharply raised spiral cords, crossed by fine, 

 crisp, axial threads which render the cords weakly gemmulate. Whorls weakly shouldered by an extra 

 strong cord situated just above the middle, 4-i, including a large dome-shaped protoconch of 1 \ whorls, 

 smooth at first, but the last half-whorl with closely spaced minute axial threads and indistinct spirals. 

 All spire-whorls with six narrow, sharply raised spiral cords, number three from the top the strongest 

 and forming the peripheral angulation. Body- whorl with twenty spiral cords, more closely spaced over 

 the middle of the base, and including five on the neck. The axial threads number about forty-five on the 



