F. B. C. Reed— New Crustacea, Isle of Wight. 117 



extended to the strong lateral carinse, which are gently arched 

 outwards and formed by a row of large sharply pointed tubercles 

 directed forwards and increasing in size from the posterior margin 

 of the carapace to the cervical groove. Outside these carinse the sides 

 of the thorax are bent down almost at right angles. 



Surface of carapace ornamented with small, widely separated, 

 sharply pointed tubercles. On the cephalon the tubercles are not 

 numerous, and are irregularly distributed, or obscurely in longitudinal 

 series ; on the thorax the tubercles are larger and arranged on the 

 upper flattened portion at equal distances apart in fairly distinct 

 longitudinal lines parallel to the lateral carinse, but on the steeply 

 inclined sides they are less regularly placed and are more closely 

 aggregated immediately behind tbe cervical groove. 



The large tubercles of the median and lateral carina? are conical and 

 sharp with the points directed forwards. 



Second antennae composed of large flattened and ridged joints (only 

 part of one joint on the left side is preserved). 



Abdomen gently convex, broad ; surface of terga flat, but bearing 

 a thin elevated longitudinal median carina; lateral edges of terga 

 slightly thickened ; surface of shell densely but finely pitted. 

 Epimeres becoming successively longer and sub-falcate; epimere of 

 second segment sub-quadrate in shape, wider than long, with straight 

 lower edge and swollen band on anterior margin, ending above in 

 articulating peg to fit into socket of preceding segment. Epimeres 

 of third and fourth segments longer than wide, sub-falcate, anterior 

 and lower margins forming a continuous curve, and posterior edge 

 serrated ; upper anterior corner swollen and cut off by oblique furrow 

 and projecting as articulating peg ; surface of shell finely pitted, but 

 less densely than rings. Perseopods compressed, slender, with surface 

 smooth and sparsely pitted. 



Dimensions. 



mm. 



Length of carapace along median line to rostral notch . . 33 '5 



Length of thorax along median line ..... 17'0 



Width of thorax between lateral carinae at posterior end . . 17'0 

 Width of thorax at point of section of lateral carinas by cervical 



groove .......... 13'5 



Width of head at anterior end between outer lateral angles . 16'0 



Width of abdomen . . . •. . . . . . 16-0 



Ilolotype. Carapace with portion of one of the right perseopods, 

 one joint of left second antennse, and with four segments of abdomen 

 attached. From the Lower Grreensand, Atherfield, Isle of Wight. 



Affinities. This species is undoubtedly allied to the London Clay 

 form Thenops scyllariformis, Bell. 1 The peculiar flattening of the 

 upper part of the carapace, the sharply bent down lateral portions, the 

 lateral and median carinse, the general development of the gastric and 

 other regions, the pair of rostral teeth, and the simple straight anterior 

 edge of the carapace are features in common. There are, however, 

 certain obvious differences which a comparison with the large series 

 of splendidly preserved examples of Th. scyllariformis from Portsmouth 



1 Bell, Mon. Foss. Malac. Crust. (Palseont. Soc), 1857, p. 33, pi. vii, figs. 1-8. 



