Dr. H. Woodward — On Fossil Shells from Sumatra. 387 



counted in the thickness of a line, and swelling out at intervals they 

 give rise to a slender spine. Dorsal valve concave, following the 

 curves of the opposite one, and similarly ornamented. Interior 

 unknown." 



Distribution : — Britain, Ireland, Belgium, Bussia, Tasmania, New 

 South Wales, and Sumatra. 



3. Productus semireticulatus, Martin, sp. PI. X. Fig. 3. 

 Davidson, Brit. Carb. Brach. (Pal. Soc. Mon.), 1861, Pt. V. p. 149, 



pi. xliii. figs. 1-11, and pi. xliv. figs. 1-4. 



The subjoined specific description is taken from Mr. Davidson's 

 monograph : — " Very variable in shape, transversely oval, sub-cylin- 

 drical or elongated; hinge-line as long as, or somewhat shorter than the 

 width of the shell ; ventral valve gibbous and variably vaulted, with 

 a shallow longitudinal median sinus or depression ; auriculate ex- 

 pansions moderately developed ; beak wide, incurved, usually covered 

 with irregular, concentric, undulating wrinkles, larger and deeper 

 upon the ears, while the entire surface of the shell is ornamented by 

 many radiating, longitudinal, rounded stria?, which become more 

 numerous towards the margin from bifurcation and interstriation 

 and from which project, at variable intervals, tubular spines of 

 sometimes considerable length. Dorsal valve moderately concave, 

 following the curves of the opposite one, and similarly sculptured. 

 Dimensions variable, some examples having attained three inches in 

 length, by four in breadth." 



Distribution : — Great Britain and Ireland, Belgium, Germany, 

 Bussia, Spitzbergen, Punjaub, Australia, North and South America, 

 and Sumatra. 



4. Productus costatus, J. de C. Sby., 1827. (Not figured.) 

 Davidson, Brit. Carb. Brach. (Pal. Soc. Mon.), 1861, Part V. p. 



152, pi. xxxii. figs. 2-9. 



Although unintentionally omitted from our Plate, we must not 

 fail to record this species from the Carboniferous rocks of Sumatra. 



We subjoin the specific description of this form given by Mr. 

 Davidson : — " Shell very variable in shape, transversely semi- 

 cylindrical, wider than long ; hinge-line about as long as the width 

 of the shell. Ventral valve gibbous, very much vaulted, abruptly 

 arched, or obscurely geniculated ; beak incurved, but not overlying 

 the hinge-line, except at its attenuated extremity, a median longi- 

 tudinal sinus or depression dividing the valve to a greater or less 

 extent into two lobes ; ears more or less developed, sloping abruptly 

 from the visceral portion, with a strong, rugged, semicircular ridge 

 on either side, obliquely placed to the hinge-line, and from which 

 project several long, cylindrical hollow spines, similar to those 

 situated close to the cardinal edge. Surface covered with a variable 

 number of strong, longitudinal, rounded ribs of unequal width, and 

 which become more numerous towards the margin from occasional 

 bifurcation or intercalation, while the whole visceral portion is 

 crossed by numerous regular concentric wrinkles, producing reticu- 

 late tuberculations. The spines are long, but variable in number, 



