122 The Molluscau Family Pknwrbidae 



Hermaphrodite Organs. The ovotcstis (go) is few-lobcd, consisting of 

 but five diverticula, which are smaller than the diverticula of the prostate. 

 It is not stated whether the lobes of the ovotestis are in a single or a double 

 row. The ovisperm duct (od) is almost as long as the uterus and oviduct 

 combined and is a very narrow tube. 



Respiratory System. The pseudobranch (figs. 5, 6, k) is shown as bifid 

 at the extremity. It is a narrow projection about twice as long as wide, 

 and probably bears the anal outlet as in other Planorbidae. The kidney 

 (fig. 5, n) is long and narrow without a superposed ridge. 



Digestive System (fig. 8). There is a long and narrow oesophagus, an 

 ovate stomach with a short pyloris and a very short blind sac (caecum, c), 

 and a long intestine which makes a loop around the stomach and another 

 around the liver, extending forward in the rectum (r) to the outlet near the 

 pseudobranch. 



The buccal sac (fig. 7) is elongated, wide at the posterior end and much 

 elongated at the anterior end. There is an unusually long radula sac (t) 

 which forms a narrow tube as long as the whole radula sac. The salivary 

 glands (s) are short, entering the radula sac by a fine tube. The jaw is 

 said to be like that of Parapholyx iPompholycodea) . 



The radula (fig. 4) formula is not given but sixteen teeth show in one 

 row in the figure which would make the formula 16-1-16. The center tooth 

 has two wide cusps which do not reach the lower margin of the base of 

 attachment. The laterals are sciuarish with a long, spade-shaped mesocone 

 reaching the lower margin of the base of attachment, and a short entocone 

 and ectocone about half as long as the mesocone. The intermediate teeth 

 have the cusps more nearly equal in size. The marginals appear wide and 

 low, the entocone and ectocone splitting into two smaller cusps. 



The information concerning this genus has been drawn entirely from 

 the original paper and figures bv Oclhner. His figures are reproduced on 

 plate 72. 



Geographical Distribution. State of Santa Catharina, Brazil. It lives 

 in damp moss on rocks over which water trickles. 



Species Considered as Valid. Acrorbis; petricola Odhner, type of the 

 genus, is tlie only species recognized. 



Remarks. Acroi^bis is apparently a very distinct group of South Ameri- 

 can Alollusca. It is not related to Carinijex or Parapholyx {Pompholy- 

 codea) as indicated by Odhner, these two genera belonging to another 

 subfamily, the Helisomatinae, in which there is a penial gland in the male 

 comjilex. It scarcely appears to belong with Choanomphalus. It is also com- 

 pared with Neoplanorbis Pilsbry, but that group is referable to the family 

 Ancylidae, not Planorbidae. 



Pilsbry has stated (1938, p. 107) that it is related to either Tropicorbis 

 or Drepanotrema. The presence of a fiagellum indicates a relationship with 

 Drepanotrema and the few diverticula of the prostate in a single series 

 indicates the same relationship, although the diverticula are more crowded 

 than has been observed in species of Drepanotrema examined. Acrorbis 

 differs from Drepanotrema in the wide form of the fiagellum, the shape of 

 the penial complex, wide for the whole length with no differentiation 

 between preputium and vergic sac, the globular spermatheca on a very 

 short duct, and the helicoid form of the shell, quite different from the 



