the Cyclostomacea of Eastern Asia. 457 



this one portion of the shell is sufficient for a division of the 

 genus. 



The section Dioryx, however, as proposed (provided the de- 

 pressly turbinate and strongly sculptured species A. crenulatus 

 be omitted) consists of a very natural and well-marked group of 

 forms, all of a somewhat globose shape, with a short sudden 

 constriction close to the peristome, and smooth (or, at the most, 

 striated), while nearly all other species are more or less strongly 

 costulated, at the inflated portion of tbe last whorl. There may 

 perhaps be some slight affinity between these peculiar globose 

 forms and the tubulated genera of the Pupinirus, especially 

 Raphaulus. 



The subgenus Dioryx, as thus defined and restricted, embraces 

 the following species : — 



A. amphora, Bens. Molmain, Burma. 



A. urnula, Bens. Darjiling, Sikkim. 



A. disiortun, Haines. Siam and Cambodia, Himalayas. 

 ^A. pilula, Gould. Hong-Kong, China; 



and a fifth species from Cambodia, obtained by M. Mouhot, of 

 which I have not learned the name. 



It will be observed that this group prevails to the eastward, 

 only one solitary representative being found on the Himalayas. 

 Doubtless other species, in considerable numbers, of all sections 

 of the genus Alyccms may yet be found in the unexplored Malay 

 and Chinese countries and in some of the large islands of the 

 archipelago*. 



The description of A. pilula is very imperfect, and I have never 

 seen the species ; but it may possibly belong to Dioryx, as no 

 transverse sculpture is mentioned as occurring on the whorls. 

 The spiral striation is peculiar. 



The remaining species of Alycaus are, for the most part, very 

 difficult to distinguish by any one special character, though they 

 may easily be grouped round different typical species. In this 

 way we may obtain seven more or less well-marked sections, 

 which may be briefly described. 



I. Type, A. gibbus, Fer. Shell perforated, subpyramidal ; 

 constriction remote from the aperture ; sculpture fine ; sutural 

 tube elongated. 



A. gibbus, Fer. Cochin China. 



A. pyramidalis, Bens. Tenasserim, Burma. 



* The great proportion of large .shells to small amongst the species 

 described from the Philippine Islands, and the different ratio found else- 

 where, where the minute forms have been carefully sought for, renders it 

 probable that the MoUuscan land-fauna even of tliose islands has only as 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. xiii. 30 



