On a neic Variety of Polydesmus coriaceus. 439 



Moussonia ahena, sp. n. 



Shell (as seen under a 1-inch objective) subulately fusi- 

 form, bronze-brown ; whorls 8, the first two smooth, rounded, 

 regularly increasing, the third proportionately broader, this 

 and the remainder strongly angled at the periphery, sculptured 

 with very oblique transverse costulse; suture well impressed; 

 columella margin tinged with reddish bronze, descending in a 

 curve and considerably outwardly dilated, bearing interiorly 

 a rather coarse, downwardly sloping, projecting tooth ; 

 labrum continuous, granular, outwardly expanded, scarcely 

 reflexed; aperture subcircular ; operculum unknown. 



Alt. 2 "75, diam. maj. 1 (about) mm. 



//<//>. Island of Beilan-Beilan, to the north of the Obi 

 Islands, Dutch East Indies (Mr. Diepenheim). 



LIII. — A new Variety of Polydesmus coriaceus, Porat, and 

 Note on a Centipede Monstrosity. By C. M. ISelbie, B.Sc. 



During the excursions held by the Belfast Naturalists' 

 Field Club in May of the present year, in celebration of the 

 fiftieth anniversary of the foundation of the club, a number 

 of Myriapods were collected and were forwarded to me for 

 examination. Among them is a specimen of Polydesmus 

 coriaceus, Porat, which belongs to a hitherto-undescribed 

 variety. 



In outward appearance it agrees exactly with typical 

 individuals of the species; it is only when the " eopulatory 

 feet " of the seventh segment are examined that any difference 

 becomes apparent. 



The most characteristic feature is the form of the extre- 

 mity of the seminal branch (fig. 1, a). This is expanded into 

 a broad double-edged blade shaped like a battle-axe, the two 

 sides being quite equal and symmetrical. Beneath the 

 opening of the seminal duet, which is furnished, as usual, 

 with a group of bristles, there is a sharp tooth or process 

 directed downwards (b) ; on the other side of the seminal 

 branch, and slightly nearer the base, there is a blunt 

 knob (c). 



The outer branch is veiy similar to that of typical 

 specimens. Near the tip it bears one small tooth on the 

 external margin (d). This, however, is not likely to be a 

 constant character, as similar teeth arc sometimes present and 



