656 



TRILOBITES OF THE UPPER SILURIAN ROCKS. 



well exposed in the drawings of Mr. C. Stokes. (See Brong. PI. 1, f. 5 A, B and C.) I have 



named this species after Mrs. Downing, to whom I am indebted for the loan of it. 



Loc. Dudley. 

 Calymene tuberculata, f. 4. 



This species has usually been referred to C. macrophthalma, from which it differs in having 



a more elevated front mid a more tuber culated central lobe of the head. 



Loc. Dudley. It occurs also near St. Petersburgh. 

 Fig. 5., fragment of a trilobite from the Wenlock Shale, probably undescribed. 

 Asaphus Stokesii (n.s.), f. 6. 



Head oval, shield much prolonged on the sides and central lobe ornamented at the base ivith 



3 tubercles. Body with 9 or 10 articulations ; caudal portion nearly semicircular ; central 



lobe slightly pointed. 



This beautiful little specimen, which belongs to Mr. Charles Stokes, is clearly distinguished 

 from every published species by its general form and by the curved and projecting sides of the 

 shield. 



I have real pleasure in naming this species after so accomplished a naturalist as Mr. Stokes, 

 who it is to be hoped may soon prepare a monograph of fossil crustaceans, concerning which 

 he possesses so much valuable knowledge. 

 Loc. Dudley. 

 Asaphus longicaudatus (n.s.), figs. 11, 12, 13 and 14. 



This trilobite differs essentially from the A. caudatus, Brong. PI. 3. f. 9., or the A. mucro- 

 natus, Dalm. Tab. 2. f. 3., both in general form and in the exceeding slenderness and length 

 of the tail. There is, however, another important distinction in the rim or outer edge of the 

 buckler, being produced anteriorly in a large protuberance. 



The most entire of our specimens (f. 12.) is a good deal mutilated in the body, and hence it 

 is impossible to describe that member accurately ; but the post abdomen, the most distinguishing 

 portion of the animal, has 15 well-pronounced articulations (the Asaphus caudatus having 10 

 to 11 only) from which the slender and pin-like tail extends in one specimen even to 2|- inches. 

 Loc. The Asaphus longicaudatus is usually found in the lower part of the Wenlock formation. 



In the specimen f. 12. (from the shale under the Wenlock Edge, near Wistanstow, Salop)^ 



the shelly matter, being partially preserved, indicates the extreme thinness of the covering 



of this crustacean. 



Fig. 11 is from the Malverns (cabinet of Mr. Bright) and figs. 13 and 14 are from Dudley, &c. 



Bumastus, Nobis. {Bumastus 1 .) 



Gen. Char. Pars anterior capitis rotundato-convexa, subsequalis : oculis lunatis, glabris, 

 remotis. Pars costalis s. corpus sulcis longitudinalibus vix apparentibus, costis decern. Pars 

 posterior maxima, rotundato-tumida, aequalis. \_Obs. Omnes testae partes ultro citroque, line- 

 arum sulcatarum subtilissimis ambagibus punctulisque confertis, insignitae.] 



Bumastus Barriensis (n.s.), PI. 7 bis. f. 3 a, b, c and d. ; PI. 14. f . 7 # and b. 



Head round {bombe) in front, margin raised, oculine protuberances large, surrounded by a 

 depression on the edge of which, over the eyes, two small ovate prominences ; in advance of the 

 eyes and toivards the margin two slight hollows. Eye approaching to semilunar, ajjparently 



1 fiovjicuTTos, uva eadem quae bumamma, genus uvse crassioris rotundique acini ; a kind of large grape. Virg. 

 Georg. ii. 102. Colum. iii. 2. 



