POLYCH^TA FROM NORTH AMERICA. ^93 



superior ones, referred to as collar seta', are distinctive, they may 

 have simple blades (fig. 13) or there may be a distinct fin-like 

 expansion at the base of the blade (figs. 7, 10 a, 11 a). In the 

 case of sinistral forms CauUeiy & Mesnil referred the former 

 to their sub-genus Romanchella, putting only those with a distinct 

 fin in the sub-genus Lceospira. In the species S. verruca and 

 S. evolutits Bush and S. medius, sp. n., however, the setse are 

 intermediate between these two types, having blades which are 

 faintly notched (fig. 14«), showing an indication of a superior 

 blade and inferior fin. Consequently I propose to do away with 

 CauUery & Mesnil's sub-genus Romanchella altogether — taking 

 Lceospira to include all sinistral forms with three setigerous 

 segments : it thus comes into line with the other three sub-genera 

 proposed by Caullery & Mesnil {cf. Table of Classification). 



The second thoracic segment has only ordinary bladed setse, 

 differing very little fi"om one species to another. 



The third thoracic segment has some ordinary bladed setse, 

 but generally also some bladed sickles as found so generally in the 

 genus Apomatus (fig. 14 e). 



In many Pacific species there are present instead of the 

 ordinary bladed sickles a peculiar shorter form which appears 

 almost fringed at the extremity (fig. 10 c). 



6. Abdominal ventral setse generally geniculate. 



7. Uncini similar in thorax and abdomen — plates with the free 



edge provided with fairly numerous fine teeth, the anterior 

 one being larger than the others. 



The following Table of Classification has been adapted from 

 that given by Caullery & Mesnil in their excellent paper on 

 Spirorhis (5) to include such of the Pacific forms as have so far 

 been studied. These authors pointed out that such a modification 

 would possibly be necessary. 



Unfortunately the majority of the new species described by 

 Bush (2, 3, 4) from California, Alaska, and Japan cannot be 

 included owing to absence of information as to the number of 

 thoracic segments. Two or three of the species are established 

 on details as to the tubes alone. 



Sub-genus Paradexiospira Caullery & Mesnil (5), 1897 

 (modified). 

 Characteristics : — - 



1. Tube dextral. 



2. Thorax with 3| setigerous segments. 



7, Spirorbis vitreus Fabr., 1780. (PI. LXXXYIII. fig. 7.) 



Serpula vitrea Fabricius (7), 1780. 



/Spirorbis vitreus Morch (20), 1863; Malmgren (14), 1867; 



Levinsen (10), 1883; Caullery & Mesnil (5) 1897; 



Moore (17), 1902 ; Bush (3), 1905. 



