with Descriptions of New Forms. 127 



Figure 5. — Mylacris anceps sp. nov. Cast-off integument of nymph. 



Figure 6. — Nymph of Mylacris elongaia Scudder. The illustration is 

 taken from the cast of the dorsal surface. The cerci of this species, as of 

 M. anceps, stand at right angles to the axis of the body. The indistinct 

 organ at the end of the abdomen may possibly be the crushed ovipositor. 



Figure 7. — Same specimen ; looking down upon dorsal surface. From 

 this view a depression indicates the outline of the body. The notch in the 

 front of the pronotum is due to erosion, the specimen having been exposed 

 to weathering agents from 1871 to 1880 (see text, p. 119). The whole 

 dorsal surface has suffered erosion during these nine years. Over the ab- 

 domen the terga have thus been partly removed, exposing the sterna. 



Figure 8. — Adult M. elongata. The much crushed head is partly exposed. 

 The pronotum, by the time the adult condition is reached, has become, as 

 usual, much rounded at the corners. The dorsal surface has been partly 

 removed to expose the legs and the abdominal sterna. 



Figure 9. — Head of same specimen. 



Figures 5-8 enlarged approximately two diameters ; Figure 9, x4. All 

 were obtained from the Coal Measures of Mazon Creek, Illinois. Originals 

 in the Yale University Museum. 



cerci are directed at right angles to the axis of the body and 

 are comparatively strong, the joints near the base being twice 

 as broad as long. The body of the insect (Figure 7) has suf- 

 fered considerable erosion, as a result of which the terga of 

 the abdomen have been removed, except at the edges, thus 

 exposing the sterna. The more rapid erosion of the integu- 

 ment of the thorax over the head and legs reveals the location 

 of these organs.* The sterna as seen in the illustration are of 

 the normal Mylacrid type. The seventh is enlarged and rounded. 

 A portion of some organ, probably the ovipositor, is seen on 

 the inner side of the seventh sternum. At the end of the 

 abdomen of both fossil and mould may be seen what appears 

 to be the two parts of the ovipositor separated and spread open 

 by crushing. 



Two adults are referred to this species. The body of the 

 adult exclusive of the head is 36 mm long. The abdomen is 

 short as compared with the long thorax. The wings are large, 

 the two pairs being of equal length and much longer than the 

 abdomen. The body is arched transversely. The tegmina 

 have a prominent humeral angle and fit down boxlike over the 

 sides of the body. The pronotum is broad and rounded at 

 the angles and has a full posterior border. The sterna of the 

 specimen figured are visible. As in the nymph, the seventh 

 sternum is enlarged and rounded, and has a depressed line 

 which may represent the impression of the thickened ridge on 

 the ninth tergum. The identification of the two adults with 



* The history of the two parts of this specimen is of interest. The mould 

 (Figure 6) was collected by Mr. S. S. Strong and sent to the Yale Museum in 

 1871 (lot No. 199). The opposite side of the nodule, evidently lost at the 

 time, remained exposed until rediscovered by Mr. Strong and sent to the Yale 

 collection in 1880 (lot No. 1400), having eroded during the intervening nine 

 years to the extent mentioned in the text. 



