Mr. A. E. Craven on the Genus Sinusigera, 141 



times and one third. Upperside of the head flat, broad, the 

 profile of the neck steeply ascen fling towards the dorsal fin. 

 Mouth transverse, rather narrow, the maxillary terminating 

 below the anterior margin of the eye. Eyes small. Opercles 

 and upper part of the cheek scaly. Scales of the body rather 

 irregularly arranged. Dorsal and anal fins rather low, the 

 rays being subequal in length and none extending beyond the 

 base of the caudal. Dorsal fin commencing above the seventh 

 ray of the anal fin. Blackish brown ; dorsal and anal with 

 small bluish spots. 



Three and three fourths inches long. Obtained by Ernest 

 Gibson, Esq., within ten miles of San Antonio, Buenos Ayres. 

 Most of the scales of the side of the abdomen have a minute 

 tubercle on their hind margin. These excrescences are pro- 

 bably developed during a certain season of the year only 



Tl* • _ • vi .1 _ __ 1 i .11 •_ i ,. . #tl. 



pot 



This species is evidently very closely allied to Cynolebias 

 *osus, described by Steindachner in the ' Wiener Sitzungs- 

 berichte,' 1877, vol. lxxiv. p. 173 ; but that species is said to be 

 from Pernambueo, has long dorsal and anal fins, and fewer 

 rays in the vertical fins. Our specimen, like that described by 

 Dr. Steindachner, is a male. 



XIX. — On the Genus Sinusigera, d* Orbigny* 



By Alfred E. Ckaven, F.L.S. &c. 



In the i Annales de la Society Malacologique de Belgique,' 



vol. xii. (1877), I published a monograph of this genus, and 

 gave the reasons that made me consider it composed of fully 

 developed shells. The two principal arguments in favour of 

 this view were the great distances from land at which they 

 were often found and the constant dimensions of each species. 



Recently, however, I have found these arguments to have 

 been wrong, and that these beautiful and elaborately sculptured 

 shells are, without any doubt, the larval 3tate of various 

 G asteropods. 





