IRIDIN A 



Genus IKimXA. I 



Testa h'walvis, hihinacido.-iu, irdiiavcrsa, p/iia miniisvc rhoiii- , 

 boidea, inttis maryaritacea, ex/us epidermide laiviijntd 

 indida, margine cardiuali recto, tominalo, crcnidnto, \ 

 vel Itev'ujato ; vulvulk anllce kiaiitlljun. 

 Shell bivalve, bhiiuscular, transverse, more or less rliom- ; 

 boidal, pearly within, covered with a smooth epider- 

 mis without, cardinal ninr^'in sti'aiglit, laminar, cre- 

 nulated, or smooth; valves gaping in front. 

 The Iridina are the tmc African type of " Naiades," 

 although not exclusively so, I. doiujnln representing the 

 river Senegal on the extreme west, and /. Nilotica the 

 great stream of the crocodiles on the north-east. The 

 rhomboidal, transverse form and straight cardinal muigin 

 are all that distinguish the Iridince from the Aiiodoiii. 

 Only one species, the /. exuiica, has the cardinal margin 

 strongly crenulated, although in I. Nilotica a slight crenu- 

 lation may be observed near the umboes in fi'ont. 



Species 1. (Mus. Cnming in Brit.) 

 Ikidin.i ELONc;at.\. Irid. tenia ubldiu/d, rhomioided, 

 sotldd, siiliiiijidtd, i-.i'ftis siihviridi, Javiyald, intns 

 sn/j/iisco-indesceidi, margine cardiuali crassiiiicido, 

 frer/gato, postice ohsoletimme crenato ; latere postico 

 paido laliori, obtusissinie angulato, margine dorsali 

 recto elevuto, margine laterali obliqiio, termiuo anb- 

 tnincato ; i/iedio complanato, margine veidrati recliiis- 

 cido ; latere antico prodncio, margine dorsali redo, ad 

 terminiim siibcitneato, margine terminoli rutmido. 

 The el()XG.\ted Iridina. Shell oblong, rhomboidal, 

 sobd, subiuflated, greeniah without, smooth, brown- 

 ish-iridescent within, cardinal margin rather thick, 

 smooth, posteriorly very obsoletely crenated ; posterior 

 side a little wider, very obtusely angular, dorsal mar- 



gin straight, elevated, lateral margin oblic|ue, end 

 subtruncated ; middle flattened, ventral margin 

 rather straight ; anterior side produced, dorsal mar- 

 gin straight, subcuneate at the end, terminal margin 

 rounded. 



SowEKBY, Genera of Shells. 



Ilab. Senegal. 



This is tile most rhomboidal of the species, even more 

 so than /. erotica. There arc only very slight crenulations 

 on the margin. 



Species :2. (Mus. Cuming in Brit.) 



IiUDlNA EXOTICA.. Irid. teitd xolidd, r/wmboided, snbcii- 

 itcij'iinni. litriijald, intns r/dtesrenti, iridescenti, mar- 

 giiii' cardiiinii recto, tube rculis postice mondiformibiis, 

 antice dciilibn, „!di,ii,is ,_ 

 obtnse aiigidiilii. hinrgnic ilnrsali i 

 elevato, Jinirijiiw liderati derlici, termino rotnndo, 

 margine ventrali postice expaiiso ; medio comprctso. 

 margine subsiiinato ; latere antico angustatu, margine 

 dor-wli depress-to, recto, termino snprd siibciineato. 



The EXOTIC Iuidina. Siiell solid, rhomboidal, subcu 

 neiform, smooth, reddish-iridescent within, cardinal 

 margin straiglit, crenated with bead-like tubercles 

 posteriorly, and with oblique teeth in front ; posterior 

 side inflated, obtusely angular, dor.sal margin straight, 

 elongated, slightly raised, lateral margin sloped, end 

 rounded, ventral margin posteriorly expanded ; mid- 

 dle compressed, with subsiriuated margin ; anterior 

 side narrow, dorsal margin depressed, straight, end 

 subcuneate above. 



L.vjiAKCK, Anim. sans vert. vol. \i. p. .571 ; 15. -M |)1- 

 204. p. 1. 



Hab. Afrie^,. 



Udcrc iiiislico injiuto. 

 do, elongtdo, sidi- 



