679 



Fig. 660. 



gards as the analogue of the amnion, or vitelline membrane, 

 of the vertebrates. This membrane is at the end of the body 

 connected with another, which in the unburst shell is external 

 to the "amnion," and lines the interior of the shell. New- 

 port compares this with the chorion of vertebrates. Before the 

 amnion is thrown off the embryo moults, 

 and six new segments appear (Fig. 650, &), 

 and minute tubercles bud out on the under 

 surface of the six and seventh rings, as at a. 

 The new segments are always developed be- 

 tween the last and penultimate ones,* as has 

 been observed in the worms, the Crustacea, 

 the spiders, and as I have observed in the em- 

 bryo of the Dragon-fly. In the young Julus 

 no legs grow out on the third segment from 

 the head, but the outlet of the oviduct of 

 the female is placed on this segment. The 

 male organs find their outlet on the sixth ring from the head. 



Julus Canadensis Newp. is brownish chestnut, ornamented 

 with a black dorsal line, and a lateral row of black dots. The 

 body consists of fifty-three segments. It is found 

 in the Northern States and Canada. 



J. multistriatus Walsh (Fig. 651) inhabits the 

 Western States. The genus Spirobolus has a much 

 larger, thicker body, and a rather small head, with 

 short antennae, often lying partially hidden in a 

 groove in the side of the head. Spirobolus margi- 

 natus Say is deep brown, annulated with red, and 

 consists of from fifty-three to fifty-seven segments. 

 The male appendages are described by Wood as 

 formed of two outer parts, and a connecting yoke-like 

 piece. 



To this family without much doubt, as Dr. Dawson 

 states, belongs the Xylobius sigillarice of Dawson 

 (Plate 1, fig. 4) from the Lower Carboniferous rocks Fi " 51t 

 of Nova Scotia. This, in its short, thick antennae, and small 

 head, rather approaches Spirobolus than Julus, though the 

 antennae are shorter, while the twelve ocelli represented in Dr. 

 Dawson's figure (Air-Breathers of the Coal Period. Montreal, 



*In the Chilopoda the new segments are intercalated between the old ones. 



