A REVIEW OF THE MYSIDACEA 



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somite, three ridges and four grooves on the second abdominal somite, 

 and three ridges and three grooves, barely perceptible, on the third 

 abdominal somite; the grooves and ridges are most pronounced on 

 the second abdominal somite, and are most marked dorsally, fading 

 away laterally. 



Figure 81. — Acanthomysis columbiae (Tattersall) : a, Antennal scale and peduncle, X 40; 

 b, endopod of fifth thoracic limb, X 40; c, telson, X 45. From a California specimen, 

 for comparison with specimens from British Columbia (Tattersall, 1933). 



(2) There is a well-marked sharp supraocular spine on the 

 carapace (fig. 80). 



(3) The carapace is produced in front into a short broadly tri- 

 angular rostral plate with an obtuse apex ; anterolateral angles acute 

 (fig. 80). 



