MUTEI.A 1365 



teriorly ; dorsal margin sloping' ; ventral margin nearly straight ; 

 anterior side flattened, rounded ; posterior side tumid, some- 

 what rostrate, sloping above, rounded below ; interior of shell 

 pale livid tlesli-color. 



Length 85, height 35 mm." (Preston). 



Type locahty, Gaboon. 

 Mntela rhotellcriana Preston, Ann. Mag. Nat. Hist., (8), IV, 



1909, p. 89, pi. IV, fig. 6. 



MuTEi^A OPAI.TJSCENS Preston. 



"Shell moderately thin, irregularly rectangular, posteriorly 

 angled, covered with a thin olive-brown periostratum, sculp- 

 tured with fine, irregular lines of growth and fine, transverse, 

 radiate striae, which are more apparent anteriorly ; umbones 

 eroded, very small, flattish ; dorsal margin ascending, ante- 

 riorly straight, posteriorly very slightly curved at the top of 

 an almost wing-like expansion ; ventral margin scarcely round- 

 ed, ver}^ slightly constricted towards the middle ; anterior side 

 short, descending obliquely, somewhat excavated ; posterior 

 side produced below, bluntly rounded ; hinge teeth obsolete ; 

 adductor scars moderately impressed ; pallial impression rosy, 

 iridescent pink ; outer margins opalescent, the radiate striae 

 very noticeable in the interior of the shell. 



Length 73, height 35 mm." (Preston). 



Type locahty. Shire River, at a point from 3 to 4 kilometres 

 to the south of Lake Nyassa. 

 Mutela opalescens Prkston. Ann. Mag. Nat. Hist.. (8), VL 



19x0, p. 62, pi. IV, fig. 12. 



"In places where the periostracum is lacking, through pro- 

 cess of erosion, the shell appears to be highly iridescent." 



Mutela cuneata Preston. 



"Shell dififering from M. opalescens by its narrower and 

 more elongate form, much more solid texture, and in the ad- 

 ductor and other scars in both valves being much more deeply 

 impressed ; the interior of the shell is more nacreous and pre- 

 sents a finely granular appearance, which is not the case in 



