110 



J.A. ALLEN AND H.L. SANDERS 



SIERRA LEONE BASIN 













Atlantis II 



146 



2842- 



2 



10"39.5'N 



17'44.5'W 



6.2.67 



ES 



31 





2891 















147 



2934 



4 



10'38.0'N 



1T52.0'W 



6.2.67 



ES 





148 



3814- 4 



10'37.0'N 



18°14.0'W 



7.2.67 



ES 







3828 















149 



3861 



1 



10'30.0'N 



18T8.0'W 



7.2.67 



ES 



GUINEA BASIN 















J. Charcot 



DS2S 



1 1261 



2 



04°21.2'N 



04°35.2'E 



7.8.71 



DS 



Walda 

















ANGOLA BASIN 















Atlantis II 



195 



3797 



46 



14"49.0'S 



09'56.0'E 



19.5.68 



ES 



42 



197 



4595 



25 



10"29.0'S 



09"04.0'E 



21.5.68 



ES 





198 



4559- 

 4566 



20 



10'24.0'S 



09°09.0'E 



21.5.68 



ES 





199 



3764- 

 3779 



3 



09'49.0'S 



10°33.0'E 



22.5.68 



ES 





200 



2644- 

 2754 



8 



09"43.5'S 



10°57.0'E 



22.5.68 



ES 



NORTH AMERICA BASIN 











Atlantis II 



2 



3752 



2 



38'05.0'N 



69°36.0'W 



22.5.61 



AD 



264 

















Atlantis II 



64 



2886 



2 



38"46.0'N 



70°06.0'W 



21.8.64 



ES 



12 



72 



2864 



9 



38T6.0'N 



71'47.0'W 



24.8.64 



ES 



Chain 50 



76 



2862 



3 



39°38.3'N 



6757.8'W 



29.6.65 



ES 





77 



3806 



752 



38"00.7'N 



69"16.0'W 



30.6.65 



ES 





78 



3828 



199 



38°00.8'N 



69°18.7'W 



30.6.65 



ES 





80 



4970 



1 



34°49.8'N 



66'34.0'W 



2.7.65 



ES 





85 



3834 



1150 3759.2'N 



69"26.2'W 



5.7.65 



ES 



Atlantis II 



124 



4862 



1 



3T26.0'N 



63'59.5'W 



22.8.66 



ES 



24 



126 



3806 



48 



39'37.0'N 



66°47.0'W 



24.8.66 



ES 



Atlantis II 



175 



4667- 



1 



36"36.0'N 



68°29.0'W 



28.11.67 



ES 



40 





4693 













Chain 106 



334 



4400 



3 



40°42.6'N 



46'13.8'W 



30.8.72 



ES 





335 



3882- 

 3919 



5 



40°25.3'N 



46°30.0'W 



31.8.72 



ES 



Knorr 35 



340 



3264- 95 



3814.4'N 



70°20.3"W 



24.11.73 



ES 







3356 













BRAZIL BASIN 



Atlantis II 156 3459 6 00*46.0'S 

 31 



GUYANA BASIN 



Knorr 25 287 4980- 72 13T6.0'N 

 4934 

 288 4417- 19 H°02.2'N 



4429 

 291 3859- 43 10"06.1'N 



3868 

 301 2487- 23 08"12.4'N 



2500 

 303 2842- 8 08'28.8'N 



2853 

 307 3862- 15 12"34.4'N 

 3835 

 J.Charcot DS05 5100 3 1046.0'N 

 Biovema 



ARGENTINE BASIN 

 Atlantis II 242 4382- 1 38'16.9'S 

 60 4402 



243 3815- 3 37"36.8'S 



3822 

 247 5208- 6 4333.0'S 



5223 

 256 3906- 8 37'40.9'S 



3917 

 259 3305- 11 3713.3'S 

 3317 



29'28.0'W 14.2.67 ES 



54"52.2'W 24.2.72 ES 



55*05.5'W 25.2.72 ES 



55"14.0'W 26.2.72 ES 



55"50.2'W 29.2.72 ES 



56°04.5'W 1 .3.72 ES 



58°59.3'W 3.3.72 ES 



42"40.3'W 19.11.77 DS 



51°56.1'W 13.3.71 ES 



52*23.6'W 14.3.71 ES 



48"58.1'W 17.3.71 ES 



52°19.3'W 24.3.71 ES 



52'45.0'W 26.3.71 ES 



Distribution. An abyssal species, found widely within temper- 

 ate and tropical latitudes at depths ranging from 2487m to 5223m. 



Shell description (Figs 12 & 13) 



Shell robust, ovate, moderately wide, ornamentated with marked 

 concentric ridges, straw-coloured periostracum; umbos prominant, 

 inwardly facing, clearly anterior of vertical midline in specimens 

 >3.0mm, more central in smaller specimens (post-umbonal length 

 c. 57% of total length); no clearly marked lunule or escutcheon, 

 but some specimens with faint indications; postero-dorsal margin 

 slight concave curve, very slightly angulate opposite limit of 

 hinge plate then steepening to posterior margin, posterior margin 

 may be somewhat flattened particularly in small specimens, ven- 

 tral margin moderately curved joining anterior and antero-dorsal 

 margins in a smooth curve, anterior and posterior limits of shell 

 dorsal to mid-horizontal line; hinge plate broad, continuous, elon- 

 gate, short chevron-shaped hinge teeth, up to 14 in posterior 

 series, 12 in anterior series, numbers varying with size of speci- 

 men, edentulous space below umbo very small; external ligament 

 short, opisthodetic, resilium microscopic, close to shell margin, 

 ventral to umbo. Maximum total length of present specimens is 

 9.8mm. 



Neilonella whoii most closely resembles N. salicensis. It can be 

 separated from the latter species by its more rounded shape and 

 greater height. The posterior shell margin is not as acute and the 

 posterior limit of the shell is more dorsal in position as compared 

 with N. salicensis. Furthermore, the post-umbonal length of N. 

 whoii is somewhat longer than in N. salicensis and the hinge plate 

 is not so broad having a smaller ratio of anterior to posterior 

 teeth. 



We name this species in honour of the Woods Hole 

 Ocenanographic Institution, through whose auspices these studies 

 were carried out. 



Internal morphology (Figs 14 & 15) 



For the most part the morphology of N. whoii is similar to that of 

 N. salicensis. Of the mantle structures, the construction of the siphon 

 is similar, although the siphonal embayment is less deep than in N. 

 salincensis. The posterior adductor muscle is oval in cross-section 

 and not much smaller than the anterior, probably reflecting the more 

 rounded shell outline of A 7 , whoii. The anterior sense organ is poorly 

 developed, the least developed of all the deep-sea nuculanids that 

 have been described to date. The gills and palps of N. whoii are 

 similar in size and form to those in N. salicensis with up to a 

 maximum of 18 gill plates and 17 palp ridges. 



The foot is large with a few moderately deep papillae at the 

 margin. The mouth lies some distance posterior to the anterior 

 adductor. The stomach is large with 9 or 10 ridges forming the 

 porterior sorting area. The hind gut makes a single loop to the right 

 side of the body, the loop being somewhat larger and more smoothly 

 curved than that in N. salicensis. The ganglia and commissures are 

 not so stout as they are in the latter species. 



Clearly Neilonella whoii is closely related to N. salicensis. 

 Although similar in form, they have markedly different depth 

 distributions, N. salicensis occurring mainly at lower slope 

 depths and N. whoii occurring mainly at abyssal depths. We believe 

 that in the past there may have been misidentifications, and speci- 

 mens of N. salicensis recorded from abyssal depths deserve 

 re-examination. 



Specimens which are narrower and relatively smaller in height to 

 length ratio than those described above (Fig. 16) are present in some 

 samples and do not occur other than with typical specimens of N. 

 whoii. In other respects they are no different in their morphology to 

 N. whoii. We consider them to be varients at the limit of a range of 

 shell outlines and not a subspecies. 





