214 PRIONOSPIO MALMGRENI. 



posterior segments capillary in the dorsal and capillary and uncinate in the ventral 

 division. Anteriorly the capillary bristles have an attenuate tip with narrow wings, whilst 

 the posterior bristles are devoid of wings. In the middle of the body the inferior ventral 

 bristles are strongly curved at the tip as well as winged. The hooks are winged, with a 

 main fang and a spike above it. 



In the anterior third of the body of Prionospio Steenstrupi a transverse section presents 

 well-developed cuticle and hypoderm,the latter especially being thick in the lateral processes, 

 and on the ventral surface external to and at the sides of the nerve-cords. The dorsal 

 longitudinal muscles are of average size, and the inner ends are slightly tapered as they 

 approach the middle line above the dorsal blood-vessel. The ventral longitudinal muscles, 

 which occupy a limited elliptical area, are also of average bulk, and in section show verti- 

 cally curved fasciculi externally and nearly horizontal fasciculi internally. In this region 

 a powerful series of fibres passes from the dorsum about the middle of the longitudinal 

 muscle, which is pierced, to the mid-ventral surface, probably in connection with the 

 proboscis, which forms a comparatively large and thick-walled organ with a foliate 

 arrangement of its mucous lining; an external coat of longitudinal and an internal layer 

 of circular muscular fibres besides its external sheath. The mid-dorsal and mid-ventral 

 vascular trunks are large, the latter lying between the ventral ends of the strong oblique 

 muscles ; these are inserted over the neural canals, which are large and situated at the 

 upper border of the nerve area, the rest of the area being hypodermic. 



Prionospio Malmgreni, Glaparede, 1868. Plate XCVIII, fig. 12— snout; Plate CXI, 

 figs. 1 — 1 b — head and body; fig. 1 c — anterior foot. Plate CIX, figs. 15 and 15 a — 

 bristles; fig. 15 b — hook. 



Specific Characters. — Cephalic region truncated anteriorly, with four eyes, two 

 anterior rounded, composed of several crystalline spheres and dark pigment, and after 

 an interval, two elongated or reniform masses of pigment. A cephalic ridge occurs in 

 the median line with a pointed process posteriorly. Body elongated like that of a small 

 Nereid, but anteriorly characteristically enlarged, whilst posteriorly it gently tapers to 

 the vent, which has two subulate cirri. Branchia3 two pairs on the third and fourth 

 bristled feet. Second and fifth bristled segments bear moderately long pinnate cirri. 

 The first ten segments have simple bristles dorsally and ventrally, the simple, yet 

 strongly curved bristles, projecting in front of the lamella and presenting a granular 

 condition of the central axis. Hooks commencing on the fourteenth or fifteenth segment, 

 a single tooth above the main fang. Length f in. Neapolitan examples 4 cm. long and 

 2 mm. broad, eighty-five to ninety segments. Colour yellowish-brown anteriorly, whitish 

 posteriorly (male). Tubicolar ; in fine mud. 



Synonyms. 



1868. Prionospio Malmgreni, Claparede. Annel. Chetop. Naples, p. 333, pi. xxii, fig. 3. 

 1910. „ Steeiistrupi, Southern. Proc. Roy. Irish Acad., vol. xxviii, p. 236. 



1914. „ Malmgreni, Mcintosh. Ann. Nat. Hist., ser. 8, vol. xiii, p. 82. 



„ „ ,, Southern. Proc. Roy. Irish Acad., vol. xxxi, no. 47, p. 102. 



