54 



J. A. ALLEN, H.L. SANDERS AND F. HANNAH 



tor muscles are relatively small and elongate and approxi- 

 mately equal in size. The gills are well-developed. The exact 

 number of gill plates is difficult to determine but at least 16 

 are present in the largest specimen. The labial palps are 

 relatively large with up to 17 ridges on the inner face and with 

 long palp proboscides. The foot is elongate with a relatively 

 narrow neck. Many subepithelial gland cells open on to the 

 sole of the foot. There is a relatively large byssal gland in the 

 heel. A small papilla is present immediately posterior to the 

 aperture of the byssal gland. The cerebral and visceral ganglia 

 are 'club'-shaped and of moderate size. The pedal ganglia, in 

 the neck of the foot, are large and elongate. 



The hind gut passes from the style sac to the left side of the 

 body and forms a loop then crosses to the right side where it 

 forms a similar loop before passing postero-dorsally to the 

 anus. The point of crossover from left to right is ventral to the 

 ligament or slightly posterior to it. A small typhlosole is 

 present along the length of the gut. 



The sexes are separate. From whole mounts, it appears 

 that the ovaries contain relatively few large ova. The testes 

 occupy a large part of the anterior half of the body with the 

 digestive diverticula dorsal to them. 



Y. americana has a similar rounded shape to Y. perplexa 

 although without the slight sinuous postero-ventral margin of 

 the latter species. Y. americana is the only species taken with 

 a single hind gut loop to the right and left of the body. 



Yoldiella subcircularis (Odhner 1960) 



Portlandia (Yoldiella) subcircularis Odhner 1960, p. 369, pi. 

 1, Fig. 1. 



Type locality. Swedish Deep-Sea Expedition, Sta. 373, 

 North America Basin, collected by R.V. Albatross, 

 24.8.1948, 28°25'N, 61°05'W - 28°05'N, 60°49'W, 

 5,500-5,987 m. 



60-| 



= 40- 



20- 



Length(mm) 



Fig. 82 Yoldiella americana. Length frequency histogram of a 

 sample from Sta. 84, North America Basin. 



Fig. 83 Yoldiella americana. Lateral views from right and left sides 

 of the internal morphology of a specimen from Sta. 84, North 

 America Basin. (Scale = 1.0 mm). For identification of parts see 

 Fig. 34. 



Type specimen. Holotype: Swedish Museum of Natural His- 

 tory, Stockholm. 



Material. 













Cruise 



Sta DepthNo 

 (m) 



Lat 



Long 



Gear Date 



WEST EUROPEAN BASIN 











Jean Charcot DS20 4226 



7 



47°33.0'N 



9°36.7'W 



DS 



24.10.72 



(Polygas) 



DS21 4190 



1 



47°31.5'N 



9°40'7'W 



DS 



24.10.72 





DS22 4144 



4 



47°34.1'N 



9°38.4'W 



DS 



25.10.72 



(Biogas IV) 



DS54 4659 



2 



46°31.1'N 



10°29.2'W 



DS 



21. 2.74 





DS55 4125 



7 



47°34.9'N 



9°40.9'W 



DS 



22. 2.74 



(Biogas V) 



S68 4550 



1 



46°26.7'N 



10°23.9'W 



DS 



19. 6.74 



(Biogas VI) 



DS75 3250 



1 



47°28.1'N 



9°07.8'W 



DS 



22.10.74 





DS76 4228 



29+ lv 47°34.8'N 



9°33.3'W 



DS 



23.10.74 





DS77 4240 



13+2v 47°31.8'N 



9°34.6'W 



DS 



24.10.74 





DS78 4706 



4 



46°31.2'N 



10°23.8'W 



DS 



25.10.74 





DS79 4715 



13 



46°30.4'N 



10°27.1'W 



DS 



26.10.74 





DS80 4720 



4 



46°29.5'N 



10°29.5'W 



DS 



27.10.74 





DS81 4715 



1 



46°28.3'N 



10°24.6'W 



DS 



27.10.74 



Jean Charcot QS02 4829 



2 



48°19.2'N 



15°l5.7'W 



OS 



2. 8.76 



(Incal) 



QS05 4296- 

 4248 



1 



47°31.3'N 

 - 47°32.2'N 



9°34.6'W 

 9°34.7'W 



OS 



7. 8.76 





QS06 4316 



6 



46°27.3'N 

 - 47°27.9'N 



9°36.2'W 

 9°36.0'W 



OS 



9. 8.76 





QS07 4249 



15 



47°31.8'N 

 - 47°31.3'N 



9°34.3'W 

 9°34.3'W 



OS 



10.8.76 





QS08 4327 



5 



47°29.8'N 

 - 47°29.5'N 



9°39.2'W 

 9°38.8'W 



OS 



11. 8.76 





WS03 4829 



10 



48°19.2'N 

 - 48°19.1'N 



15°23.3'W 

 15°22.5'W 



WS 



1. 8.76 





WS07 4281 



4 



47°30.6'N 

 - 47°31.2'N 



9°37.1'W 

 9°35.7'W 



WS 



7. 8.76 





WS08 4287 



11 



47°30.5'N 



9°33.7'W 



WS 



9. 8.76 





WS09 4277 



3 



47°28.8'N 

 - 47°27.9'N 



9°34.0'W 



WS 



10. 8.76 



