320 THE PEA EL T FRESH- WA TER M USSELS— SIMPSON. vol. xviii. 



Genus CHELIDONOPSIS, Ancey.' 



Ill 1886 Eochebrune '^ established the generic name Chelidoneura for 

 Mutela arietina, Eochebrune. The name having been used previously for 

 a moUusk of the family Philinidie, Ancey changed it to that given above. 

 I have not seen C. arietina, but a fine specimen of C. hirmido, v. Martens 

 (which Eochebrune included in his genus), is in the National Museum 

 collection, and is certainly a peculiar shell. It has the anterior dor- 

 sal part developed into a sharp point like a PHsodon or Arconai<(, and a 

 curious, elevated wing-like carina running from the beaks to about the 

 middle of the posterior end, which most decidedly gapes, with a sort 

 of diamond-shaped opening. Just in front of the posterior end each 

 ridge is developed into a tubular spine, which, in the specimen I have 

 seen, is nearly half an inch in height. One of these, in the shell 

 examined, is closed by shelly matter; the other opens into the interior. 

 The whole is covered with a thin, smooth epidermis, and in texture 

 and color strongly recalls Mutela. 



Genus SPATHA, Lea.'' 



This genus has been discussed under the head of Mutela. While 

 most of the shells have a rich coppery nacre and are smooth externally, 

 one species, which may perhaps be placed here, Spatha vignoniana, 

 Bernardi, is of a greenish lurid texture throughout, and has the sur- 

 face sculptured into a sort of reticulated and zigzag pattern, the only 

 instance I know in which a Mutelid is truly sculptured. There is a low 

 groove running down along the dorsal slope in this species, and the 

 posterior end is somewhat angulated, I believe that the African Xaiads, 

 which were referred by the older authors to Anodonta, belong in this 

 group or in Mutela, and that no true members of the former genus are 

 found south of the Sahara. While most authors agree that Spatha has 

 the mantle developed into siphons, yet in ;S'. {Anodonta) chaiziana, 

 Eang, the branchial opening is not closed.* 



According to Clessin,^ the lamiuie of the gills are united in perpen- 

 dicular rows. 



The shell of S. alata., Lea, shows slight nodules in certain specimens 

 embedded under the external nacre along the hinge line, which are no 

 doubt vestiges of taxodont teeth. 



Monceti((, Bourguignat,*' is quite likely a groiip of compressed 

 Spathas, which may possibly be worthy of subgeneric rank. Its author 

 states that the beaks are smooth; that there is a tubercular eminence 

 on the hinge line of the right valve in the cardinal region, without a cor- 



' Conchologist's Exchange, II, p. 22, 1887. 



- S. B. Nat. Fr., 1886, pp. 3-5, pi. i, figs. 1-4. 



3 Trans. Phil. Soc, VI (n. s.), 1858, p. 141, footnote. Type, S. rubena, Lea. 



•• See Lea's Synopsis of the Unioniihi", p. 79, 1870. 



s Kuster, Conch. Cab., part 234, p. 184. 



^Esp. uouv. et gen. uonv. dee Lacs Africains, pp. 34-36, 1885. 



