72 



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



60 



W\L 





40 



80 





H\L 



». .." '.. *• -,ss"-'"* TS*V H » " " "■" . 





60 









60 

 50 



PL\TL 



*<'«* - . * 







1 



2 3 



Length (mm) 



4 



Fig. 115 Yoldiella ella. Variation in ratios of height H/L. width 

 W/L and postero-umbonal length PL/TL to length against length 

 of a sample from Sta. BG VI DS 76, West European Basin. 



from the right side (Fig. 117). The hind gut then passes to 

 the mid postero-dorsal margin and thence dorsal to the 

 posterior adductor muscle to the anus. There is a relatively 

 shallow typhlosole along the length of the hind gut. Faecal 

 rods were seen cradled by the gill axes between anus and 

 the siphon. 



The kidney and heart are well-developed. The sexes are 

 separate. Animals smaller than 2.15 mm total length were all 

 immature with no obvious gonad present. The number of ova 

 varies from 16 in an individual 2.57 mm (maximum diameter 

 of ova 87 mm) to 90 in an individual 3.2 mm long (maximum 

 diameter of ova 132 p-m). In samples collected in February, 

 June, August and September in specimens of 2.15 mm and 

 above, all have maturing ova. 



Y. ella has all the characteristics of a shallow burrowing or 

 semi-submerged species i.e. a rounded, broad form, with 

 short siphons in a shallow siphonal embayment. Many speci- 

 mens bear hydroids attached to antero-ventral and ventral 

 margins. 



Two intact specimens of a species of Yoldiella in which the 

 external shell features appear to be close to Y. ella (or 

 possibly Y. enata) were taken at Sta. 199 from the Angola 

 Basin at a depth of 3771 metres (Fig. 118). We have hesitated 

 to examine the internal anatomy of these. Unfortunately 

 because of the opaqueness of the shell all that can be seen of 

 the hind gut is part of one or possibly two coils to the right of 

 the body, close to the anterior adductor. These specimens 

 could either prove to be a new species or showing variation of 

 shell form. 



Length(mm) 



Fig. 116 Yoldiella ella. Length frequency histogram of a sample 

 from Sta. BG VI DS 76, West European Basin. 



the left anterior diverticulum. This latter opens mid-laterally 

 into the stomach. A second duct from the posterior digestive 

 diverticulum of the left side opens into the left wall of the 

 stomach below the gastric tooth. The course of the hind gut is 

 first anterior and then antero-ventral to the pedal ganglia 

 before turning back on itself to pass dorsally posterior to 

 the stomach. Thereafter it forms a series of complicated 

 coils to the right side of the body the design of which can be 

 derived from a doubled strand coiled clockwise as seen 



Yoldiella fabula (new species) 



Type locality. R.V. Chain Cruise 50, Sta, 85, North 

 America Basin, 5.7.1965, 37°59.2'N, 69°26.2'W, Epibenthic 

 Trawl, 3834 m. 



Type specimen. Holotype: BM (NH) 1992037. Paratypes: in 

 collection held by J. A. Allen. 



Leda sericea Jeffreys 1879, p. 579 (in part). Two specimens 

 were found in the Jeffreys collection (U.S. Natl. Mus. No. 

 199590 (Fig. 119a) and No. 199589 (Fig. 119b)). Although 

 these are labelled L. sericea and must have been so 

 identified by Jeffreys they clearly differ from that species. 

 A specimen stored with and labelled Yoldiella expansa 

 (U.S. Natl. Mus. No. 697343 (Fig. 119c)) is also this 

 species. All these specimens were collected off West Ire- 

 land in 2500-2670 metres. 



Material. 



Cruise 



Sta 



Depth No 

 (m) 



Lat 



Long 



Gear Date 



NORTH AMERICA BASIN 



Atlantis II 



62 



2496 



4 



39°26.0'N 



70°33.0'W 



ET 



21. 



8.64 



12 



64 



2886 



1 



38°46.0'N 



70°06.0'W 



ET 



21. 



8.64 





70 



4680 



1 



36°23.0'N 



67°58.0'W 



ET 



23. 



8.64 





72 



2864 



2 



38°16.0'N 



71°47.0'W 



ET 



24. 



8.64 



Chain 50 



77 



3806 



1 



38°07.0'N 



69°16.0'W 



ET 



30. 



6.65 





78 



3828 



6 



38°08.0'N 



69°18.7'W 



ET 



30. 



6.65 





84 



4749 



4 



36°24.0'N 



67°56.0'W 



ET 



4. 



7.65 





85 



3834 



cl3 



37°59.2'N 



69°26.2'W 



ET 



5. 



7.65 



Atlantis II 

 17 



92 



4694 



1 



36°59.2'N 



69°26.2'W 



ET 



5. 



7.65 



