DICHELASPIS GRAYII. 123 



2. DlCHELASPIS Grayii. PI. II, fig. 9. 



D. scutorum segmento basalt angustiore quam seg- 

 mentum occludens; longitudine pcene dimidid: tergis bi- 

 pen?iiformibus, margin e crenato, spina posticd, manubrio 

 angustiore quam occludens scutorum segmentum. 



Scuta, with the basal segment narrower than the occlu- 

 dent segment, and about half as long as it. Terga like 

 a battle-axe, with the edge crenated and a spike behind ; 

 the handle narrower than the occludent segment of the 

 scuta. 



Mandibles with three teeth ; cirri unknown. 



Attached to the skin of a sea-snake, believed to have been the Hydeus or 

 Pelamis bicolor, and therefore from the Tropical, Indian or Pacific Oceans ; 

 associated with the Conchoderma Hunteri ; single specimen, in a very bad 

 condition, in the Royal College of Surgeons. 



General Appearance. — Capitulum much compressed, 

 elongated,, formed of very thin membrane, with the valves 

 forming round it a mere border. Valves thin, imper- 

 fectly calcified, covered with membrane. 



Scuta formed of two narrow plates at very nearly 

 right-angles to each other, one extending along the 

 occludent, and the other along the basal margin ; both 

 become very narrow at the point of junction, and are 

 there not calcified, but are evidently continuous and form 

 part of the same valve ; the basal segment is about half 

 as long and narrower than the occludent segment, flat 

 and bluntly pointed at the end; occludent segment 

 slightly curled, and therefore the whole does not lie 

 quite in the same plane; narrow close to the umbo, 

 with a very minute tooth on the under side ; apex 

 rounded. In the upper part, the occludent segments 

 leave the membranous margin of the orifice, and run in 

 near to the terga, bending towards them at an angle of 

 45° with their lower part. I was unable to distinguish 

 the primordial valves. 



