THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 20. AUGUST 1869. 



-^~) 



VIII. — On the Anatomy of Diplommatina, and its Affinity 

 with Cyclopliorus and Pupina in the Cjclophoridae. By 

 John Denis Macdonald, M.D., F.R.S., Staff- Sur^^eon, 

 R.N. 



[Plate IV.] 



The animal of the little Himalayan shell first named BuUmua 

 folUculus in Dr. Pfeiffer's Monograph of the Helicidse was 

 discovered by Capt. Hutton and Mr. Benson to differ from that 

 family in the situation of the eyes, these " not being borne on 

 the summits of the tentacula." Capt. Hutton, in his MS., 

 had actually named it Carychium costatum-, but Mr. Benson, 

 considering it to differ also from Carychium sufficiently to 

 form the type of a new genus, named it Diplommatina. He 

 chose this name from having observed that the eyes " were 

 composed of two lobes — one lobe deeply seated in the tenta- 

 culum and larger than the other lobe, which is a small black 

 point coming to the surface on the outer side of the larger 

 lobe." " Had the animal been provided with an operculum," 

 he further remarks, " it might possibly have been referred to 

 the family of Cyclostomatidai." It is clear, therefore, that Mr. 

 Benson, while admitting the affinity of his D iplommatina fol- 

 Uculus to Carychium^ considered it to be merely the type of a 

 new genus at least referable to the same group, and not to the 

 so-called Pulmonifera operculata. But the fallacy of reason- 

 ing upon insufficient data is well illustrated in the controversy 

 which followed between Mr. Benson and Dr. Gray as to the 

 cliaracter " operculo nullo " (Ann. & Mag. Nat. Hist. 1853, 

 vols. xi. & xii.). There can be little doubt, also, but the 

 belief on the part of the founder of the genus, that the eyes 

 were situated on the posterior part of the tentacula near their 

 base, gave colour to the possible absence of an operculum • 

 and such would be more conformable witli the section to which 

 Ann. & Mag. N. Hist. Ser. 4. Vol. iv, 7 



