SYSTEMATIC 163 



This seems to be a stable species so far known only from the Falkland Islands. It is characterized by 



its large, swollen body-whorl, short spire, large protoconch and lack of both nodules and colour pattern. 



It has apparently developed either as an inflated squat derivative of ancilla or more likely as a smooth 



patternless form of subnodosa. 



Other species of Adelomelon recorded from the Magellan province are: beckii Broderip, 1836; 

 ferussacii Donovan, 1824; martensi Strebel, 1906; and tuberadata Swainson, 1821. 



Genus Miomelon Dall, 1907 

 Type (o.d.) : Volutilithes philippiana Dall 



Although it has several atypical features, the shell described below is probably correctly placed in 

 Miomelon. The genus was proposed for a small Volute, 36-5 mm. in height, from 677 fathoms, south- 

 west coast of Chile. The genotype is dark olivaceous-ash colour, with a tall spire equal to the height of 

 the aperture, and the surface is sculptured with weak axial narrow folds and numerous half-obsolete 

 spiral striations. The columellar plaits number three, the anterior sinus is broad and very shallow, 

 there is no columellar callus plate and the fasciole is not margined. A very characteristic feature is the 

 form of the suture, which is deeply and narrowly channelled, but adpressed below by a distinct 

 concavity. 



The new species described below has a short spire and the sculpture is almost obsolete, but the form 

 of the suture, the plaits, absence of a columellar plate, weak, broad anterior notch and ill-defined 

 fasciole are the significant characters in accord with Miomelon. 



The Chilean Tertiary Volutes, d'orbignyana, domeykoana and gracilis Philippi, indurata Conrad and 

 triplicata Sowerby, were quoted as congeneric with philippiana by Dall (1907). The new species is not 

 unlike the New Zealand Palomelon Finlay, 1926, but that genus lacks the channelled suture, has a more 

 clearly defined fasciole and no spiral sculpture. 



Miomelon scoresbyana n.sp., PI. IX, fig. 43 



Shell small, solid, white, broadly fusiform with low conical spire 0-35 time height of aperture. 

 Whorls about six (protoconch eroded). Suture deeply and narrowly channelled and adpressed below by 

 a wide shallow concavity. Anterior notch broad and very shallow, fasciole defined only by the trend of 

 the growth lines, not marked off in any way. Posterior notch deep, narrow and constricted, forming 

 a weak sutural sinus. Plaits three, strong and of equal development, or four if the anterior thickened 

 edge of the columella is included. Sculpture consisting of very numerous but very weak axial growth 

 lines and equally numerous subobsolete spiral threads. The parietal glaze is cream coloured and extends 

 half-way across the front of the body- whorl. 



Height 48-4 mm. ; diameter 25-5 mm. 



Type locality. St. WS 816. Between Falkland Is. and Strait of Magellan, 52 09' 45" S, 64 56' W, 

 14 Jan. 1932, 150 m. 



The animal has the foot rather pointed posteriorly, is comparatively smooth, and the tentacles are 

 long and tapered (10 mm.) with the eyes at the outer side of the bases. Dall found the eyes to be 

 absent in the genotype, but the much greater depth at which it was taken (677 fathoms) would account 

 for this absence. 



The radula has not been removed, since it seems desirable to keep the only available animal intact. 

 Experience has shown that the Volutid radula is almost invariably of the same type, that is, a single row 

 of tricuspid central teeth. 



The species is named in recognition of the many novelties obtained in the trawling surveys in 



Magellan waters from the R.R.S. William Scoresby. 



