84 G. O. Sars. 



matrix. In such specimens the upper part of the carapace 

 was slightly transformed, causing the upper contour to be 

 somewhat irregularly curved; but no true ephippium was 

 formed. Male specimens were also occasionally found at the 

 same time. 



Occurrence. — Of the 2 aquaria in which this 

 form developed, the one was prepared with mud from the 

 neighbourhood of S<fo Paulo, the other with mud from 

 Ipiranga. In none of the aquaria did it occur in any con- 

 siderable number. 



Gen. Pseudalona,, n. 



Generic Characters. — Carapace greatly com- 

 pressed and of a very broad sub-quadrangular shape. Head 

 produced at the end to a well-marked deflexed rostrum. Shell 

 very thin and pellucid, but distinctly sculptured, anterior 

 part of valves with curved transverse striæ, lower edges 

 ciliated only in the middle, infero-posteal corners unarmed. 

 Lip-plate well developed. Caudal part very narrow, linear 

 in form, caudal claws slender and almost straight; spermatic 

 ducts in male debouching at the tip, in frout of the caudal 

 claws. 



Remarks. — This genus is established to comprise 

 the anomalous form described by Kurz as Alonopsis latis- 

 sima, which differs so markedly in several points from the 

 other known forms, that in the year 1890 I found it neces- 

 sary to remove it wholly from this genus, and to transfer 

 it to the genus Alonella. It does not accord sufficiently, how- 

 ever, either with this genus or with the genus Mona, in 

 which it has been placed by some other authors. Having 

 now become acquainted with another species, which, in its 



