Prof. Huxley un a Crastacaunfrum the Coal-measures. 235 



dinal ridges, and a cervical furrow extending right across the carapace. 

 The latter are sculptured somewhat after the pattern oi Nephrops, and 

 are 2 lines in length altogether. Some small fragments of subtri- 

 gonal limbs accompany the carapace. After comparing the spe- 

 cimen with the known forms of Stomapoda and Macrura, the 

 author concludes by stating that it appears to be a Decapodous 

 Crustacean presenting certain points of resemblance to Scyllarus 

 and Nephrops, but not assignable to any existing genus. Mr. 

 Gould names it Tropifer hevis. 



2. " Description of a Crustacean {Pygocephalus Cooperi) from the 

 Coal-measures." By Prof. Huxley, F.G.S. 



This new and remarkable Crustacean is represented by three 

 specimens in ironstone nodules ; each jjresenting, from the breakage 

 of the nodules, the ventral surface in relief, with the correspondiug 

 impression. Two of the specimens are the property of R. S. Cooper, 

 Esq., of Bilston, and were obtained from the shale overlying the 

 upper or thick coal-beds of that place, associated with fragments 

 of Pecopteris. The other specimen belongs to the Manchester 

 Museum, and was derived from the coal-shales at Medlock Park 

 Bridge. The animal is about 1^ inch in length; its ventral sur- 

 face presents at one extremity a quadrate disk, about |- inch long, 

 furnished anteriorly with two pairs of jointed appendages (the large 

 outer pair being antennae; the inner smaller pair, the antennules), and 

 margined by the narrow flattened edges of the carapace. The central 

 portion of the body is about \ an inch in length, and is divided into 

 a series of seven thoracic segments, composed of one medial and 

 two lateral subquadrate plates, and increasing in size backwards by 

 the gradual widening of the medial plates. Each segment is provided 

 •with a slender jointed limb on either side : the limbs are directed 

 either forward or outward ; and in one instance at least there is 

 clear evidence of a fine, jointed filament, or exopodite, attached to 

 a limb (the fifth). The posterior extremity of the specimen (consti- 

 tuted by the termination of the large abdomen, bent upon itself) is 

 much wider than the other, and has the form of a semicircular 

 disk ; the base of the semicircle forming the widest part of the body, 

 and being about half an inch distant from the centre of the curve. 

 This semicircular, caudal plate is traversed by a linear depression at 

 about the middle of its length ; another transverse depression mark 

 is near its periphery ; and, on clearing away the matrix from the 

 opposite surface of one of the specimens, this portion was found to 

 be continued underneath with a greater convexity, and with indica- 

 tions of other transverse lines of depression, bounding dorsal 

 segments. The surface of the caudal plate is also divided longi- 

 tudinally by two depressions into three broad subtriangular lobes. 



Prof. Huxley described in detail the process of his determination 

 of the above-described characters from the successive examination of 

 the several specimens ; and intimated that at first, so problematical 

 were the characters afforded by one or two specimens only, that the 

 broader extremity was regarded as possibly the cephalic buckler of an 



