julidtE. 679 



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, 6), 

 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 peiuiltimate 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 3'oung 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. 



Jidiis Canadensis Newp. is brownish chestnut, ornamented 

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

 body consists of (ifty-three segments. It is found 

 in the Northern States and Canada. 



J. mvMstriatus 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 l^dng partially hidden in a 

 groove in the side of the head. Spirobolus margi- 

 nattis Say is deep brown, aunulated 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 fiimily without much doubt, as Dr. Dawson 

 states, belongs the Xylohius sigiJlai'ice of Dawson 

 (Plate 1, fig. 4) from the Lower Carboniferous rocks ^'- ^i. 

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

 head, rather approaches Spirobolus than Julus, though the 

 antenuffi are shorter, while the tweh-e ocelli represented in Dr. 

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



^'In the Chilopoda the new segments are intercalated between the old ones. 



