282 a. M. Maplestooie: 



Canu, in " Bryozoaires fossiles de I'Argentine "\ gives a figiu'e of 

 a form which he says is Jullien's species. I do not consider that 

 this is correct, as it has no fenestrule, but it is more nearly 

 allied to /. airensis, though it differs from it, as the spinous 

 perforated processes are situated by the side of the thyrostome 

 above the iDroximal margin, and not below it, as in both /. nutrix 

 and /. airensis. 



Inversiula quadricornis, n. sp. (PI. XL VIII., Fig. 39). 



Zoarium encrusting. Zooecia oval, ventricose : surface per- 

 forated with radially, but irregularly arranged, narrow slits. 

 Thyrostouie broad, distal margin nearly straight, proximal 

 margin curved ; margins thick : two tubular upright cylindrical 

 processes on each side : a lunate, slightly depressed area below. 

 Ooecium globose (?). 



Locality. — Wilkinson's No. -1, Aire coastal beds (Dr. Hall). 



A small fragment of very peculiar structure. The zooecia 

 are very ventricose, almost globular ; the form of the thyrostome 

 is not very distinctly shown, as in the left-hand one, the right- 

 hand margin is obscured by a fragment of calcareous matter, and 

 of the right-hand one there is only a side view. The four tubular 

 processes situated close to the margins of the thyrostome are 

 characteristic. In the lower part of the specimen there is a 

 circular depression surrounded by a raised margin which I con- 

 sider is the basal wall of an ooeciumi ; the oval depression on 

 the right-hand side is apparently the basal part of a zooecium, 

 but what the small shallow round depression represents is not 

 evident. The whole structure is very unique, but I think it 

 may properly be assigned to Inversiula, as the thyrostome has 

 the proximal margin more curved than the distal one, and it 

 has the same kind of tubular sj^inous processes as the other 

 species have. 



These species are of interest because, owing to the proximal 

 margins of the thyrostomes being more curved than the distal, 

 the opercula were probably hinged at the distal, instead of at 

 the proximal, margin, as in almost all other cheilostomata. 



1 " Anales del Museo Nacional de Buenos Aires " 

 Toino xvii. (8er. 3a. t. X.), )>. 2S3, pi. vi., fi(,'. 8. 



