TEUMPET-SHAPED EYES 273 



thin, narrowly conical, ending in a single long seta. This 

 process is not met with in any other genus. The telson 

 is not incised at the apex. There is only a single species 

 known, Macropsis Slabheri (van Beneden), first, described 

 by Slabber, as a shrimp with trumpet-like eyes. It belongs 

 to British and most other European coasts. Slabber was 

 not a little struck by its organisation, and van Bene- 

 den improves the occasion by observing that in a steam- 

 engine on a railway we admire the marvel of human in- 

 dustry that has contrived its complicated parts, but that, 

 if such a locomotive were comprised in a grain of sand, if 

 we could see several of its kind deploying with precision 

 in a drop of water, we ought to be far more excited to 

 astonishment and admiration. 



Heteromysis, of which the type is the American, British, 

 and Norwegian species, Heteromysis formosa, S. I. Smith, 

 is distinguished from almost all other Mysidas by having 

 the pleopods rudimentary in the male as well as the female, 

 and also by having the third maxillipeds much stronger 

 than the rest of the legs and ending in a sort of subchelate 

 finger, which induced Sars to call the genus Ghiromysis, 

 ' the Mysis with a hand,' before he knew that it had been 

 otherwise named by Professor Smith. The telson is in- 

 cised. 



Mysidella is said to stand nearer to Heteromysis than 

 to any other genus, but with the first instead of the 

 third maxillipeds strongly built and peculiar. It has the 

 body short and stout, the scale of the second antennae 

 small, obtusely lanceolate, and fringed with hairs on both 

 margins. The upper lip is obtuse in front, and deeply 

 incised behind ; the mandibles have a large culting plate 

 which is quite simple, without any teeth. The legs are 

 small and weak, the genital appendages of the male being 

 very elongate. The pleopods in the male have the same 

 rudimentary structure as in the female. The telson is 

 short, not deeply incised, and finely aculeate on the hinder 

 portion of each lateral margin. It includes the two Nor- 

 wegian species, typica and typhlops, of Sars. 



Mysidopsis has the scale of the second antennae fringed 



21 



