Sellards — Structure of Paleozoic Cockroaches. 113 



Art. XYI. — A Study of the Structure of Paleozoic Cock- 

 roaches, ivith Descriptions of ' New Forms from the Coal 

 Measures ;* by E. H. Sellards. (With Plate I and thirty- 

 seven figures in the text.) 



Contents. 

 Introduction. 



Historical resume. 



Localities and collections. 



Acknowledgments. 



Nomenclature used in dealing with the nymphs. 



Terminology of the veins of the wing. 



Structure of Paleozoic Cockroaches. 



Head. Hind wings. Ovipositor. 



Thorax. Legs. Cerci. 



Front wings. Abdomen. Development. 



Classification and Description of Paleozoic Cockroaches. 

 Description of genera and species, including nymphs. 

 Hind wings not in connection with the front wings. 



General Considerations. 



Introduction. 



The well-known habits of many species of cockroaches, 

 their abundance, and comparatively generalized structure have 

 made them familiar insects and favorite objects of study. 

 They are a characteristic and easily recognized group, sepa- 

 rated from all other insects by a number of important struc- 

 tural differences. The body is flat and carried close to the 

 ground. Progression is by a rapid scurrying motion. The 

 tergum of the first thoracic segment, or pronotum, is large, 

 broad, and typically more or less shield-shaped, forming a 

 shelter under which the small fiat head can be more or less 

 completely withdrawn. The anal area of the front wing is 

 distinctly marked off by a strong furrow. In recent species 

 the abdomen of the female has undergone considerable modi- 



* A paper prepared in the laboratory of paleontology, Yale University 

 Museum, and constituting part of a thesis presented in May, 1903. to the 

 faculty of the Graduate School of 'Yale University for the Degree of Doctor 

 of Philosophy. As published here, it has been found necessary to omit from 

 the systematic part of the paper, as originally prepared, descriptions of some 

 of the new species, with the expectation that later these will be described 

 elsewhere. The structural and general part of the paper, however, remains 

 unchanged, except for the addition of the brief discussion of the classifica- 

 tion of Paleozoic cockroaches, and a life-size restoration of the large cock- 

 roach Archoblattina Beecheri Sellards. 



Am. Jour. Sci. — Fourth Series, Yol. XYIII, No. 104.— August, 1904. 

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