148 A renicolidae 



YOUNG STAGES. Similar in form to adults, but abranchiate. The 

 annulation may not have made its appearance, and gonads are 

 absent. 



HISTORICAL ACCOUNT. This genus and species were based by 

 Langerhans on some small worms which he found living in sand- 

 covered tubes on the north shore of Teneriffe. He stated that, 

 while these specimens exhibited unmistakable relationship with the 

 Maldanidae, the presence of gills on a number of the posterior 

 segments indicated that the worms should be placed in the family 

 Thelethusae. Langerhans briefly described the anterior end, the 

 chaetae and gills, and defined the genus thus : " Thelethusen mit 

 einfachfadenformigen Kiemen." 



Prof. Mesnil gave some details regarding the segmentation of 

 the body, the chaetae, gills and alimentary canal of a specimen of 

 B. vincenti, which he had found at St. Martin, near Cape la. Hague, 

 and in 1898 published observations on other specimens, which he 

 showed to be adult and hermaphrodite, and added a few notes on 

 the early stages of development. 



Prof. Fauvel at first 1 regarded B. vincenti as a post-larval stage 

 of Arenicola ecaudata, but, on examining other specimens, he saw that 

 they were adult. He considered B. vincenti to be anatomically an 

 Arenicola a dwarf Arenicola arrested at the " Branchiomaldane 

 stage" and therefore referred it to that genus as A. vincenti. 



Drs. Gamble and Ash worth, after stating the results of their 

 examination of two specimens of B. vincenti, concluded that the genus 

 Branchiomaldane should be retained, and the writer, who has recently 

 investigated the anatomy of the worm in detail, maintains this 

 view. 



Prof. Mesnil at first considered Clymenides incertus to be 

 autonomous, but in 1898 expressed the belief that his specimens 

 were young stages of B. vincenti. The writer has examined the 

 original specimens, which are undoubtedly young B. vincenti. 



EXTERNAL FEATURES. B. vincenti is an elongate, cylindrical 

 worm, tapering slightly in its posterior half or third (PL XT, Fig. 31). 

 It appears not to exceed a length of 20 mm., and most specimens 

 are considerably shorter about 7 to 11 mm. The prostomium is 

 bluntly conical and overhangs the mouth. It bears dorsally and 



1 Proc. 4th Internat. Congr, Zool. (1899), p. 229 ; Bull. Soc. Linn. Normandie, 

 ser. 5, ii (1899), p. liii. 



