424 PART II. SYSTEMATIC ACCOUNT 



parapodia of annelids. The dorsal side of the body he interpreted as ventral 

 and he mistakenly described a fusion of the hind end of the body with the 

 walls of the tube. The postannular region of the body was unknown to 

 Ushakov. 



In 1952 this species was redescribed in detail and figured by Ivanov, as an 

 example to illustrate the external morphology of the Pogonophora. As stated 

 earlier (p. 15), the Class Pogonophora was erected by Johansson (1937) on the 

 basis of his studies of the organization of Lamellisabella zachsi. 



The fore-part of the body is short and cylindrical, its length varying 

 between two and three times its breadth, depending on the state of contrac- 

 tion (Figs. 163v4, 5, C, 164 A). The cephalic lobe forms a much-flattened equi- 

 lateral triangle (Figs. 163 A, C, 164 A), and the base of the tentacular crown is 

 sharply separated from the region of the protosoma, consisting of 28-31 

 tentacles (Figs. 2, \63A y C, 164^4). Ushakov (1933), in his original descrip- 

 tion, suggested that the tentacles were united by a very delicate membrane, 

 but in reality there is no such membrane, the tentacles being firmly united to 

 one another by means of a common cuticle, such as is also found in L. 

 johanssoni and in Spirobrachia spp. Ushakov is also mistaken in his statement 

 that "large cartilage cells" were present in the tentacles. Between the bases 

 of the two ventral tentacles there is always a small orifice which puts the 

 intertentacular cavity into communication with the exterior (Fig. 1635). 

 The distal ends of the tentacles are free for a considerable length and the 

 internal surface of the tentacular cylinder bears a dense thicket of long 

 pinnules, which are absent only from the basal part of the crown. On each ten- 

 tacle the pinnules are arranged in three longitudinal rows and alternate regu- 

 larly with the pinnules of the neighbouring rows. The bridle has pronounced 

 ridges and the black keels are strongly thickened at the ventral end where 

 they may reach 60-70/x in width. On the lateral sides of the body they taper 

 quickly and on the dorsal side become very thin indeed (Fig. 1635, C). 

 Neither ventrally nor dorsally do the keels fuse. In front of the bridle on the 

 ventral side there is often a more or less broad but shallow dorsal furrow in 

 which the epidermis presents an uneven surface. The hind edge of the fore- 

 part of the body is a simple annular groove with a small dorsal notch and with 

 a more or less deep ventral bay (Fig. 1635). The male genital papillae are 

 large and rounded. 



The metameric division of the trunk has more or less metameric, paired 

 papillae, each bearing a pulvillus with a horseshoe-shaped cuticular plaque 

 (Figs. 2, 1635). As noted by Ushakov (1933) the number of "horseshoes" 

 varies between 17 and 22 pairs in different individuals, but if all the more or 



