846 MR JAMES RITCHIE ON 



Synonymy of Barentsia benedeni (Foettinger). 



Pedicellina benedeni, Foettinger, Arch. Bio]., vol. vii., 1886, p. 301 et seq., pi. x. 



figs. 1-7, 9-15, 17-22. Id., Loppens, Ann. Soc. Roy. Zool. Malac. Belgique, t. xli., 



No. 3, 1906, p. 300. 

 Arthropodaria benedeni, Ehlers, Abh. Kon. Ges. Wissens. Gottingen, Bd. xxxvi., 



1890, p. 144. 



IV. Systematic Relationships of the Hull Specimens. 



The Hull specimens seem to take a place intermediate between that of Barentsia 

 benedeni and B. gracilis. In general appearance the greater agreement is with 

 the former, for the Hull specimens possess a robustness of build which is lacking in 

 B. gracilis ; the proportions of the parts of the stem, and in especial the perfect 

 differentiation of the internodes into rigid and definite flexile sections, are very similar 

 in both, while in each buds may arise from the internodes. But between B. 

 benedeni and the Hull specimens there are numerous differences, the values of which 

 as indications of specificity are difficult to estimate in the absence of information 

 regarding the variation of such forms. The calyx of the Hull specimens is generally 

 very much smaller ; the number of tentacles is fewer, and these are colourless instead 

 of reddish-brown ; the brain is trapezoid instead of biscuit-shaped in transverse section. 



There is greater similarity between the Hull calyx and that of B. gracilis, for, 

 although the size of the former is less even than that of the latter, the characters 

 mentioned above agree in both. On the other hand, the differences in the robustness 

 of the stem, in the development, definiteness, and finish of the parts of the internodes, 

 are very evident. In B. gracilis, both in the English and Belgian specimens, the 

 rigid, chitinous portion of an internode bends outwards here and there in the form of 

 a very small papilla, sometimes perforated by a minute pore. The presence of similar 

 pores has been described in Barentsia (Ascopodaria) macropus by Ehlers (op. cit., 

 p. 34 et sea., pi. ii. fig. 24), and in Barentsia (Gonypodaria) ramosa by Miss Robertson. 

 They do not occur in Barentsia benedeni, nor are they present in the Hull specimens. 



From both species the Hull specimens differ in lacking any trace of the oval 

 aggregates of granules which form a characteristic feature of the muscular expansions of 

 the internodes of B. benedeni, and which also appear, though less prominently, in the 

 stems of B. gracilis. The oval granular masses are confined to the central portion of 

 the muscular expansions, but differ greatly in numbers in the various internodes. In 

 B. benedeni, they are absent from the two distal internodes, and appear in the third, 

 few in number, and arranged in a hollow cylinder lining the interior of the muscle 

 layer. In internodes further from the calyx the number increases, until, in those 

 towards the base of the stem, the centre of the muscular expansion is filled with a 

 dense, closely packed mass, which, under low magnification, produces the appearance of 



