310 Dr. H. Woodward — A new Er yon from the Lias. 



backwards. The margin along the branchial region is entire, broadly 

 and gently rounded, its border finely serrated, having five or six rather 

 larger spines at irregular intervals. The carapace contracts slightly in 

 breadth towards the cervical ridge l where the first marginal indentation 

 is seen, in front of which is a small, rather obtuse, marginal tooth, 

 marked by a slight notch in front and by a branch of the cervical 

 'furrow' behind ; this is succeeded (anteriorly) by a second roundly 

 incurved marginal tooth, twice the breadth of the last one, with 

 a rounded border and sharply pointed spine directed forwards and 

 marked off anteriorly by a well-defined notch and by the superior 

 branch of the cervical ' furrow V The margin again expands slightly, 

 and then curves rapidly inwards until it forms with a spine the outer 

 angle of the orbital fossa. The anterior frontal border (with the 

 antennules and antennse) has been much crushed and can only be 

 imperfectly defined. The eyes are not preserved, but on the right side 

 there is a portion of one of the large chelse seen in section lying in the 

 orbital fossa (s). "Width of the anterior border of carapace, 3 cm. ; 

 width across the broadest part of the carapace (behind the cervical 

 ridge 1 ), 9 cm.; width at posterior border, 6cm.; length of carapace 

 along the dorsal line, 7 cm. The cervical ridge occupies its centre and 

 forms a concave curve backwards 15 mm. in breadth, being SJcra. 

 behind the anterior and 3 J cm. in front of the posterior border. 

 It bifurcates at 10 mm. on either side of the dorsal line, enclosing 

 between its branches the two tooth-like serrations on the lateral 

 border. Two curved furrows 2 cross the posterior portion of the 

 carapace, the inner pair at 15 mm. distance on either side of the 

 straight dorsal line at the hinder border, but converging to 10mm. at 

 the cervical furrow ; the outer pair are more faintly marked. The 

 dorsal ridge and the two lateral lines nearest to the dorsal line 

 (marked by slightly larger tubercles) extend from the cervical furrow 

 to the anterior margin of the carapace. 



Traces of the basal joints of the large anterior pair of chelate legs 

 are seen on the anterior part of the carapace at c, and one of the 

 chelae is seen upon the slab in its normal position (ch). The three 

 anterior abdominal segments still remain attached to the cephalo- 

 thorax, and measure together 3| cm. in length and 5 cm. in breadth. 

 Each segment is broadest near its margin, and is strongly corrugated 

 transversely, the back and front ridges of each segment converging on 

 the dorsal line, and each segment is marked by a very prominent 

 tubercle which we see as a hollow on the under-side. These transverse 

 ridges and furrows give attachment to the muscles for flexing the 

 abdominal segments and the rhipidura or tail-fan in swimming. The 

 central portion of each segment is ornamented with minute tubercles, 

 but the interlocking and overlapping anterior and posterior borders 

 are smooth. 



1 This would, on the exposed upper surface of the carapace, be seen to be 

 a furrow, but is here seen from beneath as a ridge. 



- But for the fact that we are looking at the nnder-surfaee, both the 

 dorsal and lateral furrows would appear as ridges upon the upper surface of the 

 carapace, whilst the cervical furrow (which is really a furrow) appears as a ridge 

 when seen from underneath. 



