PALEONTOLOGY 



stegocephalian amphibians known as Microsauri. It was described by 

 Dr. A. Smith Woodward in the Geological Magazine for 1891 (p. 211), and 

 belongs to a genus of which the first known specimens were collected by the 

 late Sir William Dawson from hollow Lepidodendron trunks in the Nova 

 Scotian Coal Measures. Of that genus it is the only known British repre- 

 sentative. 



The second and more typical Lancashire labyrinthodont, which was 

 obtained by Mr. Wild in the Middle Coal Measures of the Bardsley Colliery, 

 is at present undescribed. It is regarded by Mr. Bolton as probably referable 

 to the Carboniferous and Permian genus Archegosaurus. 



Passing on to the Coal Measure fishes, and commencing with those 

 primitive Palaeozoic sharks known as Ichthyotomi, the first specimen to record 

 is a spine from the Lower Foot Mine at Littleborough, identified by 

 Mr. Wellburn with Pleuracantbus cylindricus^ a species known elsewhere from 

 the Coal Measures of Scotland, Northumberland, Yorkshire, and Staffordshire. 

 Mr. Bolton includes in his lists P. lavissimus, P. undulatus, P. erectus, and 

 P. denticulatus ; the first of these is a good species, but the second is a synonym 

 of the first, and the other two are founded on spines. The allied genus 

 Diplodus is represented in the county by two species, D. gibbosus and D. tenuis, 

 of which the first alone is recorded from Littleborough ; D. tenuis has a distri- 

 bution very similar to that of Pleuracanthus cyclindricus, but D. gibbosus is not 

 known to occur in Scotland. Among the more typical sharks, the Palaeozoic 

 family of Petalodontidae, characterized among other features by the pavement- 

 like dentition of a peculiar type, is represented by several species in the Car- 

 boniferous of the county. Firstly, we have Ctenoptychius apicalis, typically 

 from Staffordshire, recorded by Dr. Smith Woodward as a Lancashire fish ; 

 while Mr. Bolton mentions a second species, C. lobatus, typically from Scotland. 

 Mr. Wellburn includes in his Littleborough list a member of another genus, 

 Callopristodus pectinatus, first described from the Scottish coal-fields. To another 

 family of Palaeozoic sharks, the GochKodontidai, whose nearest relationships are 

 probably with the Port Jackson sharks (Gestraciontula), belongs Pleuroplax 

 ranking of which remains are recorded from Littleborough, the species having 

 a wide distribution in Britain. The Northumberland species P. attheyi appears 

 in Mr. Bolton's list. Next on our list comes a species of the genus Sphenacan- 

 tbus (belonging to the family Cestraciontidce), which Mr. Wellburn considered 

 might be new ; it is represented by a spine from the Lower Foot Mine of the 

 Littleborough district, said to be unlike any hitherto described. Mr. Bolton's 

 Lancashire list includes, however, only the widely distributed S. hybodoides. 

 Certain other specimens from the Littleborough district are of the type of 

 those to which the ill-defined name Stemmatodus has been applied, such speci- 

 mens being probably dermal ossifications belonging to Pleuracanthus or one of 

 the allied genera. The imperfectly-known genus Tristychius or Petrodus is 

 represented in the Yoredale rocks near Todmorden. A single spine from the 

 Littleborough district is assigned to Acanthodes wardi, a species typically from 

 Staffordshire belonging to an altogether peculiar group of Palaeozoic sharks 

 collectively known as Acanthodii ; remains of the same genus are recorded by 

 Mr. Morton from St. Helens, and the species occurs in Mr. Bolton's list. 

 Following this come two representatives of the lung-fishes, or Dipnoi, belong- 

 ing to the extinct genus Ctenodus, which takes its name from the somewhat 



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