DICHELASPIS PELLUCIDA. 127 



Peduncle. — Its narrowness and transparency are its 

 only two remarkable characters. 



Mouth. — All the parts closely resemble those of 

 B. Grayii, but being in a better state of preservation I 

 will describe them. The labrum is highly bullate, with 

 a row of minute teeth on the crest, placed very close 

 together in the middle. Palpi small, thinly clothed with 

 spines ; mandibles extremely narrow, hairy, with four 

 teeth, but the lower tooth is so close to the inferior 

 angle, as only to make the latter look double. Maxillae, 

 with a very deep broad notch, dividing the whole into 

 two almost equal halves ; in the upper part there are 

 three main spines. 



Cirri. — The first pair are placed at a considerable dis- 

 tance from the second pair ; they are short with equal 

 rami, and rather broad segments furnished with a few 

 transverse rows of bristles. The five posterior cirri have 

 singularly few, but much elongated segments, bearing 

 four pair of spines : the two rami of the second pair are 

 alike, and differ only from the posterior cirri in a few 

 of the basal segments having a few more spines. 



The Caudal Appendages are twice as long as the pedi- 

 cels, and nearly half as long as the whole of the sixth 

 cirrus ; they have a small tuft of long thin spines at their 

 ends, and a few in pairs, or single, along their whole 

 length ; at first I thought that they were multi- articulate, 

 but after careful examination I can perceive no distinct 

 articulations ; I have seen no other instance of so long 

 an appendage without articulations. 



Diagnosis. — This species differs from D. Grayii in all 

 the valves being shorter, so that their points only just 

 cross each other ; but this, I conceive, is an unimportant 

 character. In the scuta, the basal segment is here nar- 

 rower, but the point of junction of the two segments 

 wider than in that species ; in the terga, the edge of the 

 axe is smooth instead of being crenatecl, and the handle 

 and the point behind are of a rather different shape ; in 

 the carina the imbedded basal disc has not shoulders and 



