374 BULLETIN OF THE 



They differ from specimens from the United States in having a firmer and 

 less transparent shell, and a little differently shaped propodite to the second 

 pair of thoracic legs in the male ; hardly enough to warrant the establish- 

 ment of a new species when one considers the variability of the species 

 within the limits of the United States. 



After an examination of a large number of Hyalella dentala and H. iner- 

 mis from Utah, I am satisfied that they are but varieties of one species. The 

 form with dorsal teeth on the first and second abdominal segments is very 

 probably synonymous with Amphitoe aztecus Saussure* and Allorchestes 

 Knickerbockeri Bate,f as pointed out by Professor Smith himself. 



This species (var. inermis) was also collected by Mr. Agassiz at San An- 

 tonio, Peru, in saline water, 3,300 feet above the sea; nitrate district of 

 Pisagua. The specimens differ slightly from the type described from the 

 United States in having the fifth pair of thoracic legs a little shorter in pro- 

 portion to the sixth pair. 



It may be well to announce here the discovery of this species during the 

 voyage of the " Hassler " at Puerto Bueno, Smyth Channel, Straits of Ma- 

 gellan. The specimens do not differ from var. inermis from the United 

 States. The ticket accompanying the specimens does not indicate their 

 fresh-water origin; but Count Pourtales tells me that some animals were 

 collected at Puerto Bueno by Dr. Steindachner and himself in a fresh-water 

 pond and an outlet stream. The Allorchestes were probably among them. % 



* M&noire sur divers Crustacea nouveaux du Mexique et des Antilles, p. 58, PI. V. 

 Fig. 33, 1858. 



f Catalogue of the Specimens of Amphipodous Crustacea in the Collection of the 

 British Museum, p. 36, PI. VI. Fig. 1, 1862. 



| Among the Crustacea collected by the Thayer Expedition in Brazil are two species 

 of Allorchestes. One is represented by a unique female specimen taken from a canal 



' Allorchestes dentatus, var. gracilicornis, head. 



at Campos by C. F. Hartt. It differs from A. dentatus, var. inermis, only in the second 

 pair of antennas, which are half as long as the body and twice as long as the first pair ; 



