268 NEREIS PELAGICA. 



little after the three lobes and the two setigerous processes are complete, except that 

 behind the anterior third the tips of the lobes become more pointed, and posteriorly the 

 cirri are elongated. The posterior feet also diminish in size and become more transparent, 

 and the heterogomph bristles, both upper and lower, are proportionally stronger. 



Proboscis of the typical two regions in extrusion (Fig. 58). From the maxillary 

 project the two dark brown, horny jaws, having five to seven teeth. Dorsally behind 

 them is on each side a crescent of dark brown paragnathi (II) formed of three rows 

 of points. Between these are two paragnathi (I), one anterior to the other. On 

 the eminence in front of each palpus is a group of four long teeth which probably 

 correspond with VI, whilst a narrow triangle with the apex in front probably represents 

 V, though devoid of paragnathi. Slightly behind the foregoing a line of paragnathi (VII) 

 trends to the ventral surface and joins VIII. Ventrally a belt of maxillary prickles (IV), 

 broader at the outer or ventral edge, occurs below the jaws in a similar position to the 

 dorsal crescents, but with a different arrangement of the prickles. In the median line is 

 a transverse belt of paragnathi (III), which in some forms a central group of about eight 

 and a short lateral crescent of three prickles. The basal division of the organ has a 

 conspicuous belt (VIII) extending more or less from the dorsal elevations across the 

 lozenges formed by the lines of the region. The larger prickles are generally in a single 

 row in front, whilst a belt of more numerous, minute prickles — diminishing from front to 

 rear — occurs behind. 1 



Ejpitokous form. — In the males, which are found from January to June, the head is wide 

 and the eyes are larger; the dorsal cirri of the first seven feet are thickened throughout 

 the greater part of their length, the short tip being filiform. The ventral cirrus in the first 

 four or five feet is also enlarged. At the seventeenth foot the change from the nereid to the 

 heteronereid condition commences with increased vascularity; a dorsal lamella, a ventral, a 

 large inferior setigerous lamella, and a superior subsetigerous lamella all being developed, 

 with fan-like groups of swimming bristles. The dorsal cirrus has a row of prominent 

 papillae along its lower edge. Sperms extend far forward to the anterior or nereid region. 

 The colour is greenish anteriorly, posteriorly pale or cream-coloured from the sperms, 

 except in those first mentioned, Avhich are pale anteriorly. The tip of the tail is pinkish 

 from the vessels. 



Female. — Deep russet-brown and iridescent in February from ova, which are of a 

 faint salmon-colour. The tips of the palpi are dull brownish-orange like the proboscis. 

 The same whitish patch occurs in front, between and behind the eyes. In September the 

 feet become very vascular, so as to give a deep red aspect to the sides, whilst their tips 

 are pale. At St. Andrews pelagic females have been found, but none have been observed 

 from other British localities. 



Synonyms. 

 1746. Nereis pelagica, Linnasus. Fauna Suec, Ed. 2, p. 2096. 

 1758. „ „ idem. Syst. Nat,, Ed. 10, i, p. 654. 



1762. ,, „ Baster. Opusc. subsec, Tom. ii, p. 133, Tab. 6, f. 6. 



1 Grube characterizes the proboscis of the group containing N. pelagica and N. diver sieolor as 

 having VI of four or five in the form of a quadrangle or a cross, and Y absent. 



