. Bulletin of the British Museum (Natural History) Zoology. Bull. Br. Mus. nat. Hist. (Zool) 55(2): 123-171 Issued 26 October 1989 Studies on the Deep Sea Protobranchia: The Subfamily Ledellinae (Nuculanidae) r^ITISH museum 1 "iNATUBAL HISTORY) J. A. ALLEN & FIONA J. HANNAH | . 2 NOV 1989 University Marine Biological Station, Millport, Isle of Cumbrae Scotland KA28 OEG 1 K8DCCEMTFI. CONTENTS \ -:a| htm Introduction 123 Abbreviations to text figures 124 Family Nuculanidae Adams & Adams 1858 124 Subfamily Ledellinae Allen & Sanders 1982 124 Ledella Verrill & Bush 1897 124 Le
. Bulletin of the British Museum (Natural History) Zoology. Bull. Br. Mus. nat. Hist. (Zool) 55(2): 123-171 Issued 26 October 1989 Studies on the Deep Sea Protobranchia: The Subfamily Ledellinae (Nuculanidae) r^ITISH museum 1 "iNATUBAL HISTORY) J. A. ALLEN & FIONA J. HANNAH | . 2 NOV 1989 University Marine Biological Station, Millport, Isle of Cumbrae Scotland KA28 OEG 1 K8DCCEMTFI. CONTENTS \ -:a| htm Introduction 123 Abbreviations to text figures 124 Family Nuculanidae Adams & Adams 1858 124 Subfamily Ledellinae Allen & Sanders 1982 124 Ledella Verrill & Bush 1897 124 Ledella pustulosa pustulosa 125 Ledella pustulosa marshalli 131 Ledella pustulosa argentinae 135 Ledella pustulosa hampsoni 138 Ledella sublevis 139 Ledella jamesi 140 Ledella lusitanensis 143 Ledella sandersi 146 Ledella similis 146 Ledella verdiensis 148 Ledella oxira 148 Ledella galathea 151 Ledella solidula 152 Ledella acuminata 153 Ledella ultima 155 Ledella parva 165 Ledella sp 167 Distribution patterns 168 Morphological evolution 169 References 171 SYNOPSIS Fourteen species of Ledella occurring in the Atlantic are described, five of which are new species, namely, L. jamesi, L. lusitanensis, L. sandersi, L. similis and L. verdiensis. Species of the subfamily Ledellinae are usually small, less than 7 mm total length, with shells that are solid, concentrically ridged, ovate, medially or submedially rostrate, and with an amphidetic predominantly internal ligament. The morphology of Ledella is very conservative, the only organ that shows any marked variation in form is the hind gut. Five different configurations of the hindgut occur and these can be derived by radiate or sequential evolution from the primitive condition in which the hind gut forms a single deep loop on the right side of the body. Although the three most widely distributed species are confined to abyssal depths, endemic species also occur at abyssal depths in individual basins. The most common species, ,
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