DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



Tindariopsis aeolata (Dall 1890) 



Type specimen. Holotype, USNM 95436. 



Type locality. U.S. Fish Commission Sta. 2754, East ofTobago, 

 1 1'40'N 58"33'W, 1609m. 



Cited specimen. BMNH 1 99506 1 . 



Malletia (Tindaria?) aeolata Dall 1890, 252. 

 Tindaria (Tindariopsis) aeolata Dall 1898, 582. 

 Tindariopsis aeolata James 1972, 97, figs 57-59. 



Material: 



Cruise 



Sta 



Depth No Lat 

 (m) 



Long 



Date 



Gear 



GUYANA BASIN 



Knorr25 299 1942-4 07"55.I'N 55"42.0'W 29.2.72 ES 

 2076 

 301 2487-5 08'12.4'N 55"50.2'W 29.2.72 ES 

 2500 



The type specimen has been examined by us. 



This species occurs from mid to lower slope depths in the tropical 

 western Atlantic in the Guyana and Caribbean Basins and the Gulf of 

 Mexico. Depth range: 1609-3466m. 



Shell description (Figs 27 & 28) 



Shell small, subquadrate, rostrate, ornamented with marked concen- 

 tric ridges; periostracum pale yellow; umbos moderately large, 

 posterior to midline (post-umbonal length 45-48% of total length), 

 facing inwards, slightly separated by external ligament; distally 

 antero-dorsal shell margin horizontal, then curves smoothly and 

 steeply to anterior margin, postero-ventral margin sinuous, ventral 

 margin somewhat flattened, postero-dorsal distal margin slopes 

 gently to limit of hinge plate then curves sharply to rostral point, 

 latter rounded and somewhat eroded in large specimens, more 

 pointed in smaller, rostrum in mid horizontal plane in small speci- 

 mens and dorsal to it in large specimens, limit of anterior margin 



Fig. 27. Tindariopsis aeolata. External lateral view of the right valve and 

 the hinge plate of the left valve of the holotype, from U.S. Fish 

 Commission station 2754. USNM 95436. Scale = 1mm. 



Fig. 28. Tindariopsis aeolata. External lateral views of the right side of 

 shells of differing size to change in shape with growth, a, from Knorr 

 station 301 and b, from Knorr station 299 from the Guyana Basin; c, 

 external dorsal view of a shell also from Knorr station 299. Scales 

 = 1 mm. 



ventral to the mid horizontal plane; hinge plate stout, small edentu- 

 lous space between tooth series, 9 chevron-shaped teeth in anterior 

 series and 10 in posterior series in largest specimens; ligament 

 amphidetic, external except for small resilifer at margin ventral to 

 umbo, external part thickened, particularly so in large specimens. 

 The maximum length of the present specimens is 5.8mm. 



In lateral view the rostrum, although dorsal to mid horizontal line, 

 is reminiscent of Ledella, while the robust external ligament is more 

 reminiscent of Spinula. 



Internal morphology (Fig.29) 



The siphonal embayment is relatively shallow and the contained 

 siphon is similar to that of T. acinula. The adductor muscles are 

 moderately small, ovate in cross-section and equal in size. The foot 

 is large, with a divided sole fringed with large papillae. The 'byssaF 

 gland is moderate in size. The palps are very large with many ridges 

 (c 26 in the largest specimen) and the palp proboscides are broad. 

 The gills are small with 1 1 gill plates in the largest specimen. The 

 kidney is long and narrow. The nervous system is of typical 

 protobranch design. The ganglia are relatively large and, in contrast, 

 the commissures are unusually slender. 



The mouth lies some distance posterior to the anterior adductor 

 muscle (see below). The oesophagus opens on to the anterior face of 

 a moderately large stomach. The latter lies almost vertical within the 

 posterior part of the visceral mass. The hind gut is very small in 

 diameter and takes an extraordinarily complex course through the 

 body. There are two loops to the left side of the body (Fig.29B) and 

 one major loop to the right side of the body, all three pass from one 

 side to the other ventral to the umbo. There is also a complex series 

 of loops anterior and to the right of the stomach. This morphology 

 has not been encountered before in the protobranch bivalves and is 

 very different from that seen in T agatheda. Yet, it is debateable 



