

ORDER ENTOMOSTRACA. 



The grand subdivisions of the Entomostraca here adopted, are based 

 on the character of the mouth, and are distinguished as follows : — 



I. Gnathostomata. — Os mandibulis maxillisque regularibus armatum, 

 sessile et non rostriforme nee mobile. 



II. Cormostomata. — Os mandibulis tenuibus et ssepe spiculiformibus 

 armatum, rostriforme ssepeque basi mobile ; raro videtur inerme. 



III. Merostomata. — Os basibus pedum plurium in locis mandibu- 

 larum et maxillarum instructum. 



The propriety of this arrangement has been discussed on pages 12 

 and 13. The Limuli constitute the last section, being closely related 

 to other Entomostraca. It may even be doubted whether this third 

 subdivision should not be merged in the first, as the transition in the 

 structure of the mouth from the first to the third, is very gradual, as 

 will be shown beyond. "We would here refer to a concluding chapter 

 in this volume for some additional observations on the relations of the 

 Entomostraca to the higher Crustacea. 



