Dr. U. Woodward — On a New Fossil Isopod. 531 



Viewed from the front (see PI. XV. Fig. lc) the strongly-marked 

 trilobation of the cephalon is still more clearly seen. The epistomial 

 plate is observable attached to the frontal margin of the glabella; 

 resembling somewhat a short heraldic " label," with two pendant 

 square ends. Traces of the antennules and antennae occupy the 

 lateral frontal margin of the cephalon, which is deeply excavated on 

 each side for the articulation of their broad basal joints. 



The eyes stand out from the antero-lateral angles of the cephalon, 

 the superciliary border being formed by the projecting margin of 

 the lateral lobes, of the head and the inferior border by the encircling 

 lateral margin of the first thoracic segment, which here unites with 

 the front margin of the head-shield (cephalon). 



Thoracic segments. — There are seven thoracic segments between 

 the cephalon and the abdomen ; each segment is very strongly 

 corrugated, and is narrower in the centre along the median dorsal 

 line, but more expanded towards its free margins or epimera. The 

 first thoracic segment is, without doubt, united to the cephalon, and 

 curves around the lateral margins of the head-shield ; the second 

 thoracic segment is also curved somewhat forward at its epimeral 

 margins ; the third and fourth are nearly straight ; the fifth, sixth, 

 and seventh segments curve rather backwards, being nearly twice 

 as wide at the epimera as on the median dorsal line. The epimeral 

 border of each segment is distinctly marked off and defined by 

 a clear lateral line of division crossing all the segments from near 

 the outer angle of the eye on each side to the anterior outer angle 

 of the abdomen (see PI. XV. Figs, la, lb). The posterior margin 

 of the cephalon and that of each thoracic segment, has a narrow 

 raised border, separated by a furrow from the rest of the segment, 

 forming the line of articulation between each segment and the one 

 immediately succeeding it ; this union is further strengthened by 

 the enarthroidal articulation of each segment with its neighbouring 

 one near its epimeral border. 



Owing to the decorticated condition of the posterior portion of 

 the fossil, any indication of the former divisions of the coalesced 

 segments in the abdomen which may have existed in the crust are 

 wanting ; but we have evidence on the cast of two, or more, strong- 

 protuberances on this region of the body. The abdomen is two and 

 a half times as broad as it is long, being extremely narrow laterally, 

 somewhat rhomboidal in outline, and must have had spines along 

 its posterior border. Behind the abdomen the body terminates in 

 a " telson," or caudal shield, nearly three times as broad as it is 

 long, but some of the margin of this shield has probably been lost. 

 It had two powerful sub-median spines near the anterior border, 

 and one in the centre near the posterior extremity, which is acutely 

 pointed. The sides are strongly curved and hollowed out for the 

 reception of the flat curved inner lobe of the lateral appendages 



epimera of the two thoracic segments are completely united, and show uo traces of 

 their original distinctness ; these epimera are always largely developed, and com- 

 pletely inclose the cephalic shield on both sides (Frank E. Beddard, iieport on the 

 Jsopoda collected by H.M.S. " Challenger," during the years 1873-7(3. Part I. 

 Serolis: Zoology, vol. xi. 1884, p. 8). 



