CYCLOBRACHIA AURICULATA 367 



/. Cyclobrachia auriculata Ivanov (Figs. 145-7) 



Ivanov, 1960c: 6, 93, 97, 215, 216-19, 266, Figs. 87, 145-7. 



Amongst 13 fragments of tube of this species, unfortunately only a single 

 animal was found, a male with a badly damaged tentacular crown of which 

 only the base remained. The specific name Cyclobrachia auriculata refers to 

 the possession of auricular lappets on the dorsal side of the mesosoma. The 

 rather short, massive fore-part of the body is perceptibly stouter in the front 

 half of the mesosoma (Fig. 145Д В, C), and the protosoma is considerably 

 narrower than the mesosoma and divided from it by a very obvious groove. 

 There is, in addition, a dorsal post-tentacular groove, and as may be seen in 

 a side view, there are only nine tentacles arranged in a single series to form a 

 closed circle. The small cephalic lobe forms an equilateral triangle. The 

 brownish keels of the well-developed bridle, situated in the front half of the 

 mesosoma, are rather stout, especially on the ventral side where they are 

 fused together (Fig. 145^4, C). The cutaneous ridges of the bridle are pro- 

 nounced and on the dorsal side they expand to run into the swollen bases of 

 the cutaneous auricular lappets. These latter are very characteristic and are 

 not found in any other pogonophores. Each lappet is a triangular outgrowth 

 pointing forwards and there is a moderate-sized gap between them (Fig. 

 1455). The keels of the bridle do not reach into the mid-dorsal region and in 

 the single available specimen the two dorsal ends are differently situated, due, 

 in all likelihood, to an individual variation from the norm. On the left the 

 keel makes an S-bend at the base of the lappet before running on to it, while 

 the right keel is situated just in front of the lappet, outside its limits, on the 

 surface of the mesosoma (Fig. 1455). The front part of the mesosoma in 

 front of the auricular lappets has both a clear, mid-dorsal furrow, which 

 forks into two behind the lappets to outline a slightly swollen dorsal area 

 (Fig. 1455), and a shallow longitudinal depression on the ventral surface 

 (Fig. 145 A). The boundary between the mesosoma and the metasoma is a 

 straight transverse groove, which, on the ventral side, is masked by a pair of 

 large male genital papillae (Fig. 145.4, C). 



The ventral sulcus in the front part of the metasoma is very broad, but not 

 deep, and each of the comparatively small, rounded adhesive papillae, which 

 run along each side, carries a dark-brown cuticular plaque (Fig. 145.4). A 

 prominent feature is the large number of these papillae, amounting to 113 

 on the left and 109 on the right. The cuticular plaques in this part of the 

 trunk are kidney-shaped and the front thickened edge of each one is a broad 

 dark-brown curved bow, with rounded ends. The remaining part of the 

 plaque is very thin and transparent (Fig. 145/)). The whole plaque measures 



