56 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



ON THE ANATOMY OF TURRITELLA COMMUNIS, Risso. 



By W. B. Randles, B.Sc, etc. 

 (From the Zoological Laboratory, Royal College of Science, London.) 



Bead 11th January, 1900. 



PLATE VI. 



Considerable interest has recently centred round the TurritellidaB 

 on account of the suggested affinities between some of the members 

 of this family and the extinct Murchisoniidse. Mr. Marrat, of 

 Liverpool, who was the first to draw attention to the resemblances 

 between the two families, went so far as to suggest that certain 

 living Turritellidse more properly belonged to the genus Murchisonia. 

 The study of these doubtful Turritellidse has been further carried 

 on by Miss Donald l in connection with her researches on the 

 Murchisoniidre. 



The genus Murchisonia is universally regarded as referable to the 

 Diotocardia, i.e. to the most primitive group of living Prosobranchs, 

 whereas Turritella is known to belong to the Monotocardia, and 

 consequently to be more specialized. If, however, the above 

 authorities are correct in their surmise that these notched Turritellidae 

 are living representatives of the genus Murchisonia, then two 

 questions arise, viz. : ( 1 ) is the family Turritellidae a very primitive 

 one, much more so than is generally supposed, and having affinities 

 to the Diotocardia? or (2) are we including in the Turritellidae two 

 entirely distinct types, one of which, comprising the forms with 

 a notched peristome, belongs to the Diotocardia, and the other to 

 the Monotocardia ? 



To enable us to settle these questions, for we have no knowledge 

 whatever of the anatomy of the notch-bearing Turritellce, we should 

 need a great deal of material, which is at present unobtainable. In 

 order, however, to be prepared in the future for the study of these 

 forms, it is necessary first of all to know something of the anatomy of 

 a typical Turritella, and, as at present the information on this point is 

 somewhat meagre, it has been deemed advisable to describe briefly the 

 anatomy of Turritella communis, Eisso. 



The material for this investigation was collected by Mr. M. F. 

 Woodward while working at the Marine Laboratory of the Royal 

 Society of Dublin, then stationed at Inishbofin, co. Galway ; further 



1 Quart. Journ. Gcol. Soc, vol. xliii (1887), pp. G18 and 619; vol. liv (U 

 pp. 45-72; Proc. Malac. Soc. Loudon, ante, pp. 47-55. 



