1873.] J. Wood-Mason — On Nephropsis Stewarti. 41 



of the anterior margin of the epistoma when it bends boldly upwards and 

 backwards upon itself passing into the well-defined semicircular depression that 

 bounds the lateral convexities described above. The cardiac region is broader 

 than long, very convex transversely and bounded on each side by a densely-tu- 

 berculated elevation which running backwards, downwards, and forwards along 

 the line of the granulated rim of the branchiostegite, and finally bending 

 upwards almost opposite the origin of the second pair of abdominal appen- 

 dages, passes again into the swollen anterior boundary of the omostegite ; 

 the ovoidal area thus limited off is more sparsely beset with tubercles and 

 presents a marked depression on its anterior half. 



The rostrum carries on each side a most acute spine directed upwards 

 and forwards, and curved slightly inwards ; and above presents two roughly 

 granulated ridges coalescent towards the tip but divergent at the base ; 

 beyond the spines it is canaliculate on each side, above and below, and each 

 lateral ridge is fringed with long hairs ; below it is carinated and coarsely 

 granulated at the base. A faint linear impression, continuous with the 

 groove between the ridges on the rostrum, passes along the middle line of 

 the carapace almost to its posterior border ; situated in this line, and marking 

 the anterior limit of the convex gastric region, lies an almost erect spiniform 

 tubercle. 



AntenncB and antennules. — The peduncles of these appendages lie as 

 in Neplirops Norvegicus in the same horizontal line, and their inner margins 

 are ciliate. The basal joint, or coxocerite, of the former is extremely short, 

 and wants the apical spine in Nephrops^ but the perforated conical process 

 on its inferior surface is remarkably salient ; the second is devoid both of 

 the prominent spine into which, in JSfepJirops, its distal and external angle 

 is produced, and of the squamiform appendage or scale seen in all the other 

 recognized genera of Astacidce* and developed to such an extraordinary 

 degree in Carideous Crustacea ; one or two small folds or impressions between, 

 or upon, the second and fourth joints being all that remains of the antennal 

 scale, and of the rudimentary joint that in JSfephrops corresponds to the 

 moveable spine of Astacits.] 



* The antennal scale in Astacoides escaped tlie notice of Guerin wlio founded his 

 genus on its supposed absence. 



t There appears to be no doubt but that the antennal scale is the representa- 

 tive of the outer of the two appendages borne upon the protopodite at an early 

 stage of embryonic life, and, if the moveable spine in Astacivs and its undoubted 

 homologue in the antennoe of Nephrops represent the inner of these appendages, then 

 must the three distal joints of the peduncle with the fla-oHum be looked upon, as Dr. 

 Fritz Miiller looks upon them, as a new formation (Noubilduug) and no longer as be- 

 ing in serial homology with the five distal joints of the other appendages, e. </., of an 

 ambulatory leg, which represent the endopodite, the exopodito being completely ab- 

 orted or represented at most, as RoUestou remarks, by the annular coustriotiou ou 







