14 MR. C. TATE REGAN ON THE 



■of the rib, and then backwards on the proctal side of the axial 

 bone, ending in a nodule of bone that lies near the axial bone at 

 the level of the articulation of the ctenactinium. 



Longitudinal muscles of the priapium. — These are four in 

 number and each^ is more or less fusiform in shape. In front 

 of the priapial ribs these muscles, with the intermuscular connec- 

 tive tissue and the axial bone, constitute the whole body of the 

 priapium (excluding the pulvinulus) (text-fig. 4 A). 



Ctenactinial muscle. — This is the largest of the longitudinal 

 priapial muscles ; it originates at the posterior end of the upper 

 anterior ridge of the axial bone and is inserted on the proximal 

 end of the ctenactinium. For most of its length its inner surface 

 lies against the whole proctal face of the main crest and the lower 

 face of the lateral ridge of the axial bone. 



Outer muscle of the aproctal side. — This originates at the 

 anterior extremity of the axial bone and runs back on the 

 aproctal side between the anterior ridges of that bone, and then 

 on the aproctal side of the main crest until the inner muscle 

 intervenes ; it ends posteriorly at the level of the anus in the 

 connective tissue that lies between the floor of the glandular 

 groove and the lateral ridge of the axial bone. 



Inner muscle of the aproctal side. — Anteriorly this is inserted 

 between the outer muscle and the main crest of the axial bone ; 

 it runs back in contact with the cvest and above the lateral ridge, 

 and then on the aproctal side of the priapial ribs, pleuro-priapial 

 muscle, and intestine ; it is attached posteriorly to the lower and 

 proctal surface of the terminal style of the axial bone just above 

 the vas deferens, which is here crossing to the proctal side below 

 the axial bone. 



Muscle of the proctal side. — This originates on tlie anterior 

 end of the upper edge of the main crest of the axial bone, and 

 runs backwards at first above and then at the proctal side of the 

 ctenactinial muscle ; it lies on the proctal side of the priapial ribs 

 and intestine and behind them at the side of the inner aproctal 

 muscle ; it ends in the connective tissue that lies above the ter- 

 minal style of the axial bone and between the descending portion 

 and the enlarged terminal part of the vas deferens. 



4. Neostethus bicornis, sp. n. (text-fig. 11). 



This species is more slender than A^. lankesteri and has 36 ver- 

 tebrae (16-17-1-19-20) instead of 34 or 35. There are 13 to 

 15 anal rays, and 35 to 37 scales in a longitudinal series. 



A male of 25 mm. is not fully adult, but its priapium (text- 

 fig. 11, B) difiers from that of ]^. lankesteri in three important 

 characters: (1) there are two ctenactinia (c^.), both on the 

 aproctal side ; (2) the efferent groove (ef.) extends downwaixls 

 to the ventral surface of the posterior end of the pi-iapium ; and 

 (3) the seminal papilla [p.) opens into the effei-ent, not the 

 .glandular groove. The ctenactinia have not attained their full 



