onsxiiosTOMA, 299 



" The characters which serve to distinguish Opisthostoma fuir- 

 banki from 0. nilgiricum are : — 



1. The greater cxsertion and smaller exceutric deflecliou of the 

 two apical whorls of 0, fairhanli. 



2. The simple expanded peristonie and subtrigonally rounded 

 aperture — 0. nihjiricKin having a nou-expanding duplicate peri- 

 stome, the outer portion retro-relict, and a circular aperture. 



3. The more distant sculpture. 



4. The manner of curvature of the last whorl, the posterior 

 bend of which is much more acute in the pi'esent species. In 

 0, nilgiricum the posterior half of the sigmoid curve of the last 

 whorl is more open than the semicircular curve nearer the 

 apei'ture, the nmbilicus being fully exposed within the former, 

 tn 0. fairbanki the anterior curve is the more open, and the last 

 whorl just in front of the posterior half of the cui-ve passes across 

 and completely conceals the umbilicus. 



"I have with some difficulty, detected in 0. fairbanki the minute 

 decussating stria) observed by my brother between the costulations 

 in 0. niUjiricum. They are very difficult to see, even under a high 

 power and strong light, and appear to be frequently obsolete. 

 I cannot detect them in my specimen of 0. nihjiriciun, which is 

 in good order. 



" The blnntly trigonal form of the aperture in 0. fairbanki does 

 not appear to be quite constant ; the mouth in some specimens is 

 nearly round."' {Jiiauford.) 



456. Opisthostoma macrostoma, Blanford. 



Opisthostoma macrostoma (Beddome MS.), Blanford, J.A. S. B, 

 xxxviii, 1869, p. 139, pi. 16, tig-. 7 ; Ilauley & Theobald, Conch, 

 lud. 1875, pi. 117, ti<>-. 9 ; L^feitfer, Men. I'neuni. Suppl. 3, 187o, 

 p. 69; Theobald, Cat. Shells Brit. India, 1876, p. 43; Nevill, 

 Hand List, i, 1878, p. 284 ; Crosse, Jouru. Couchyl. xxvii, 1879, 

 p. 196 ; Aucey, Bull. Soc. Malac. France, iv, 1887, p. 274. 



Opisthodoina [EuoinstJiostonm) macrostoma, Kobelt & Molleudorff, 

 Nachr. Deuts. Malak. Ges. xxx, 1898, p. 134 ; id.. Cat. Puemn. 

 1899, p. 54. 



Opisthostoma ( Opisthostoma) macrostoma, Kobelt, Das Tierveicli, 

 Lief. 10, 1902, p. 413. 



Original description : — '" Testa perforata, conoideo-ovata, albida 

 vel pallide rubella, subdistanter oblique filiformi-costulata, sub 

 lente spiraliter minutissime et confertissime striata. Spiraelevato- 

 conoidea, lateribus convexis ; apice acutiuseulo ; sutura valde 

 irapressa. Anfr. o^, convexi, apicales normales non diviantes, 

 penultimus vix major, ultimus confertius costulatus, brevissime 

 coustrictns, antice sigmoideo-deflexus. L'mbilicus ab anfractu 

 ultimo non-occultus. xlpertura retrorsa sub-rotunda, fere verti- 

 calis ; peristoma brevissime ad anfractos duos, peindtimura et 

 ante-penultimum, adnatum, duplex, internum continuum e.x- 

 pansiusculum, externum, expansum breviter interruptum. 



