The Scottish Naturalist. 185 



ACANTHOCARIS nov. gen. 



Externa antenna erassa, primo segment permagno; intemarum 

 antennarum pars inferior (ex tribus segmentis) longior eadem ex- 

 ternarum antennarum parte,. et duabus multi-articulatis appendi- 

 culis instructa. Pedes omnes monodaclyli, a parte a?iteriore re- 

 trorsum dccrescentes. Oculi eoniei, pednnculis brevibus validis im- 

 positi. Testa (sive clypeus dorsalis) a parte poster iore altissima, 

 sulco tenui i?i dorso post regio?ie?n gastricam arata, septem spinis 

 in margine posteriore ar/nata, et ab anteriore parte in rostro obtuso 

 decurvato desinens. Sternum quoddam post test am usque ad ex- 

 tremam secundi abdominis segment i partem porrigitur ; intra hoc 

 sternum respirandi instrumenia locata sunt. Abdomen pane cy- 

 lindritum. Telson (sive lamella caudalis media) bifurcation, 

 utroque aculeo spina valida immobili instructo, armatum senis 

 mobilibus spinis per utrumque latus dispositis. 



External antennae thick, first segment very large ; basal portion of the internal 

 antennae longer than that of the external, and furnished with two multi articulate 

 appendages. Feet wholly monodactyle, decreasing from before backwards. 

 Eyes conical, set on short stout foot-stalks. Carapace deepest posteriorly, with 

 a slight furrow on the dorsal aspect behind the gastric region, and armed with 

 seven spines on the posterior margin, and terminating anteriorly in an obtuse de- 

 curved rostrum. A sort of sternum extending behind the carapace to the extrem- 

 ity of the second abdominal segment, within which sternum the respiratory 

 organs are placed. Abdomen nearly cylindrical. Telson bifurcate, each point 

 armed with a strong immovable spine, and six movable spines along each side. 



ACANTHOCARIS LlVINGSTONEANA ft. Sp. 

 {Plate IV., Fig. B.J 



Carapace. — Smooth, with a slight transverse hollow on the 

 dorsal aspect, and armed with seven sharp spines on the pos- 

 terior margin. Nostrum. — A single depressed rather obtuse 

 spine bent down between the eyes. Eyes. — Conical, covered 

 with a sort of cap in front, and about one third longer than 

 their short stout peduncles, the whole extending slightly 

 beyond the' joint of the antennal scale. External ant, una. — 

 With the first segment three-fourths the length of the scale, 

 rounded and slightly swelled in the centre ; second, one-third 

 the length of the first, movable portion stout at the base but 

 becoming abruptly slender. As it was imperfect I cannot give its 



