176 Mr Henry Goodsir on a mw Genus, 



structure is also essentially different. In Cynthia the four last 

 of these members are each composed of a very large bilobate 

 scale, supporting at its apex two taper articulate fins, strongly 

 ciliated with plumose setas ; from between these originates an 

 opaque organ which bifurcates, its two extremes of unequal 

 length being rolled inwards, the one over the other.'' Mr Ed- 

 wards considers that these last are the branchial apparatus. 



The two animals which are presently to be described, pre- 

 sent characters of such a nature as to require the formation of 

 a new genus for their reception. This will constitute a con- 

 necting link between the true Opossum Shrimp and the genus 

 Cynthia of Thompson. The subabdominal fins of the genus 

 Mysis, are composed of one short joint, bearing a plumose 

 fringe. The subabdominal fins of the two animals under con- 

 sideration are of a mixed character, the two first and the fifth 

 are like those of Mysis, the third and fourth are like those of 

 the Cynthia in so far, that the plumes are double, while at the 

 same time these two fins are triarticulate. Thus approaching 

 to the genus Noctiluca of Thompson. 



Genus TAe?nhto. 

 Generic Characters. — Superior antennae, armed with a scale. First, se- 

 cond, and fifth seg-ments of the abdomen bearing fins like the Mysis ; 

 third and fourth with the peduncles, biarticulate, and each peduncle 

 giving off two branches ; the external branch of the fourth very long 

 and slender, semi articulated. 



Fig. 4., pi. II. 



T. Longispinosa. — Superior antennal scale of the same length, as the ter- 

 minal joint of its peduncle, armed at its extremity with a thick tuft of 

 hairs. Inferior antennal scale twice as long as its peduncle ; fringe 

 not strong. Third subabdominal fin, with its internal branch, minute. 

 Internal branch of the fourth, with a few long hairs from the extremity 

 only. External branch reaching to the extremity of the caudal fins. 

 Internal caudal fin truncated. 



Long, I of an inch. — Hab., Frith of Forth. 



Description. — The whole body of a dark- yellowish or greenish colour. 

 Eyes large, reaching to the extremity of the peduncle of the inferior 

 antennse. The reticulated portion black, and produced backwards in- 

 feriorly. Bostrum very short, but sharply pointed. First joint of the 

 peduncle of the inferior antennae very strong, the two following slen- 

 der ; the setaceous portion of the antennae arising from the extremity 

 of the last. The scale arises from the inner nnd superior part of the 



