12 Description of Genera and Species. 



of it. None of them have been observed to be serrated or crenulated. The smaller area 

 in front of the cervical fold shows an arched gastric portion surmounted by the median 

 keel, which is continued forward into a slender rostrum about one-tliird of the length of 

 the trunk. The rostrum is further strengthened by two flanking keels, and has at least 

 one spine on each side of the median terminal one. The lateral angles made by the 

 confluence of the rostrum with the anterior margin of the carapace are well rounded off 

 to form orbits, and there is a supra-orbital spine marking the termination of that part of 

 the dorso-lateral keel lying in front of the fold. This keel is also placed upon an 

 embossed eminence. Chiefly owing to the crushing and crowding of the parts during 

 fossilisation, no evidence has been obtained as to whether there is an antennal spine, 

 though certain indications seem to suggest its presence. The edges of the carapace in 

 the space between the position of the antennal spine and the fold seem to be puffed out, 

 and as seen from beneath, as in iig. 5, M. 482 P,* form a little recess within, 

 similar to that seen in Gnathophausia, and doubtless for the same purpose, viz., to 

 hold the peculiar exognathite of the second maxilla, remains of which are preserved in 

 specimen M. 4807^ (fig. 7*). 



In the larger area behind the cervical fold the median keel occurs near the 

 anterior end, only being most pronounced just behind the fold and dying down rapidly 

 when traced backwards, and disappearing altogether before one-third of the distance to 

 the posterior margin is reached. There is no appearance of either the keel or a median 

 spine at the posterior margin. The dor.so-lateral keels are most pronounced in front 

 just behind the fold, and can be traced right back to the posterior margin. The two 

 lateral keels on each side begin at the fold and, diverging gently for a time, converge 

 towards the rounded-off posterolateral angles of the carapace. Behind the cervical 

 fold the carapace is edged with a handsome fluted band which passes round the back- 

 wardly-directed, rounded lappets and the concave posterior margin. So deeply cut out 

 is this posterior part of the carapace that while the posterior angles lap over the epimera 

 of the first tail segment, the whole breadth of the last trunk segment is left bare in the 

 mid-line of the back. As stated alcove, no trace of median backwardly-directed spine 

 has been observed. 



The tail (figs. 1, H, 4, 5), which is about the same length as the trunk, is well arched 

 and almost cylindrical, but tapering backwards, and is constructed, like that of the true 

 caridea, of six segments forming complete rings with epimera, and a seventh terminal 

 one or telson in which the anus is situated (figs. 3, 4, 5), and which has therefore a 

 right to be considered a true segment and not a medial appendage. According to this 



* Geological Survey registration number. 



