Bull. not. Hist. Mm. bond. (Zool.) 62(2): 101-132 



Issued 28 November 1996 



Studies on the deep-sea Protobranchia 

 (Rival via): the family Neilonellidae and the 

 family Nuculanidae. 



J.A. ALLEN 



University Marine Biological Station, Millport, Isle of Cumbrae, Scotland, KA28 OEG 



H.L. SANDERS 



The Woods Hole Oceanographic Institution, Massachusetts, 02543, USA 



CONTENTS 



Synopsis 101 



Introduction 101 



Family Neilonellidae 102 



Neilonella salicensis (Seguenza 1877) 103 



Neilonella hampsoni (new species) 107 



Neilonella corpulenta (Dall 1881) 108 



Neilonella whoii (new species) 108 



Family Nuculanidae 1 1 1 



Subfamily Ledellinae 1 1 1 



Ledella acinula (Dall 1890) Ill 



Ledella aberrata (new species) 1 14 



Tmdariopsis agatheda (Dall 1889) 116 



Tmdariopsis aeolata (Dall 1890) 119 



Subfamily Nuculaninae 120 



Nuculana acuta (Conrad 1831 ) 120 



Nuculana commutata (Philippi 1 844) 123 



Nuculana vestita (Locard, 1898) 124 



Propeleda carpenteri (Dall 1881) 125 



Propeleda louiseae (Clarke 1961) 127 



Propeleda paucistriata (new species) 128 



Discussion 130 



References 131 



Synopsis. The morphology and distribution of four deep-water protobranch species of the family Neilonellidae and ten deep- 

 water protobranch species of the family Nuculanidae are described. These include four new species. The evolution of the 

 nuculanoid siphonate form is discussed. 



INTRODUCTION 



This is the ninth paper in a series on the deep-sea species of 

 Protobranchia of the Atlantic. While a few undescribed species of 

 families reported upon in earlier papers have been found in later 

 samples and remain to be described, this paper is the last of our 

 major descriptive accounts of the morphologies of this exceptionally 

 important group of deep sea bivalves. 



In this paper we give an account of a number of nuculanacean 

 species belonging to the families Neilonellidae and Nuculanidae 

 present in our collections from the deep Atlantic. Related species 

 already described are refered to only when essential for descriptive 

 and comparative purposes. Unlike previous papers in this series 

 most of the species described below are known, but only from their 

 shell characters. This is in part due to the fact that many species come 

 from upper-slope depths, and thus more likely to have been sampled 



in the past, and in part due to the fact that they are relatively large and 

 thus less likely to have been lost due to the coarseness of nets used 

 in earlier expeditions. Many earlier descriptions of the shell are far 

 from adequate and new descriptions are given. 



We have followed the methods and approach of earlier papers in 

 this series (Allen and Hannah, 1989; Allen and Sanders, 1973, 1982; 

 Allen, Sanders and Hannah, 1995; Rhind and Allen, 1992; Sanders 

 and Allen, 1973, 1977, 1985). From stereoscopic microscope ex- 

 amination of shell features and whole mounts of the body stained in 

 haemotoxylin, from dissected specimens and serial sections stained 

 with trichome techniques, we give detailed descriptions of the shell 

 and internal morphology of key species. Descriptions of related 

 species are limited to points of difference and importance. 



Much of the material was taken by ourselves on numerous 

 expeditions by research vessels of the Woods Hole Oceanographic 

 Institution. These include the Atlantis', Atlantis II', 'Chain' and 

 'Knorr'. Other samples were taken by JAA on the British research 



©The Natural History Museum. 1996 



