434 PART II. SYSTEMATIC ACCOUNT 



Fig. 168C. The longest fragments of tube reach 34 cm in length, but the 

 whole tube must be much longer. The stoutest tube of all is 1 -7 mm in 

 diameter at the front end and 0-125 mm at the hind end. 



The 18 tentacles of the tentacular crown contrast with the 29-31 found in 

 Lamellisabella zachsi and the 22 in L. ivanovi. The exceptionally powerful 

 bridle catches the eye immediately, and its keels are almost twice as broad and 

 considerably higher than in L. zachsi, and, moreover, they are fused together 

 on the ventral side, in contrast with their condition in the latter species. 

 Again in contrast with L. zachsi, both the girdles are narrowly broken on the 

 dorsal side. The spermatophores of L. johanssoni are sharply distinguished 

 in shape from those of L. zachsi and are only half their size. The sperm, 

 moreover, are arranged obliquely and not longitudinally as in L. zachsi. The 

 tube of L. johanssoni is segmented while that of L. zachsi is smooth. Other 

 distinctions between the species are presented in Table 6. 



Material: nine specimens (amongst which four were semi-decomposed), 

 together with a great number of pieces of tubes. 



Locality: the northern part of the Japan Trench. 



Depth: 6156-6207 m. 



3. Lamellisabella ivanovi Kirkegaard (Fig. 169) 



Kirkegaard, 1956b: 183-4, Figs. 1, 2 (as L. zachsi); Kirkegaard, 1961: 7-10, Figs. 1-3; 

 Ivanov, 1960c: 4, 97, 242, 251-3, 266, Fig. 169. 



[Because of an unfortunate delay in the publication of Kirkegaard's paper 

 (1961) Ivanov's description of this species was the first to appear under this 

 name, for he had been instrumental in pointing out to Kirkegaard that his 

 material did not in fact belong to L. zachsi, as first described (Kirkegaard, 

 1956b) but formed a new species. These authorities were thus in correspon- 

 dence and Ivanov was able to examine Kirkegaard's material and to read his 

 manuscript. He incorporated the following description in his book in the full 

 belief that Kirkegaard's description would appear first.] 



This species is known from a single, badly preserved, incomplete specimen 

 found by Kirkegaard in a collection of benthos from the Bay of Panama in 

 the eastern Pacific Ocean and ascribed by him to L. zachsi (Kirkegaard, 

 1956b). As shown, however, by comparison with the other species of Lamell- 

 isabella, the Panamanian specimen appeared to be distinct (Kirkegaard, 1961). 



L. ivanovi is distinguished by the possession of 22 tentacles and by the 

 peculiar structure of the keels of the bridle, which consist of a pair of clear 

 cuticular rods with a row of dark cuticular bodies attached behind them 



