8 G. 0. Sårs. 



Remarks. — This form differs in a number of well- 

 marked characters from the 2 hitherto known species, 

 L. australis G. O. Sars and L. occidentalis Birge. For inst- 

 ance, the upper ramus of the antennæ (see fig. 5) has a much 

 greater number of natatory setæ, and the caudal part (see 

 fig. 6) is prominently characterized by the coarse serrations 

 of its dorsal edge, as also by the presence of 3, instead of 



2 secondary spines at the bases of the caudal claws. More- 

 over, the long posterior ramus of the shell-gland present in 

 both the other species is entirely absent. The form recorded 

 by Mr. Richard from Rio Grande do Sul as L. australis may 

 perhaps be this species. The solitary specimen examined 

 by him was, however, in such a bad state of preservation, 

 that it did not admit of a more accurate examination. 



Biological Ob ser v at ions. — A few specimens of 

 this interesting form appeared last summer in one of my 

 aquaria, which had previously been exposed for some time 

 to the direct rays of the sun, whereby the temperature of 

 the water had attained a very high degree. Believing that 

 such a high temperature would be beneficial to the thriving 

 of this form, the aquarium was kept in the same situation 

 for several days. This seems, however, to have been fatal 

 to its development, for the existence of this form was of com- 

 paratively short duration, and after some time the specimens 

 gradually disappeared, without having multiplied to any 

 noticeable extent. I had previonsly, however, secured 2 or 



3 specimens, which were carefully preserved for renewed 

 examination. One of these, an apparently adult ovigerous 

 female, was immediately subjected to a close examination 

 beneath the microscope, and all the figures reproduced on 

 the accompanying plate were made from this specimen, while 

 yet alive. It only carried 2 summer-eggs of the usual 



