Herbert L. Hawkins — Studies on the Echinoidea, etc. 165 



recognized in the original specimen of P. umbrella, Agass., 1839. 

 The bad preservation of the type makes reference of other specimens 

 to it dangerous. If the species usually called P. dilatatus (the second 

 name given by Agassiz to his former P. umbrella) is really that of 

 1839, then it may be stated with confidence that it is not synonymous 

 with P. semisulcatus. I have shown above that, whatever might be 

 the result of such an inquiry, the name semisulcatus is either 

 independent of, or must supersede, that of umbrella. 



Having established the legitimacy of the specific name Pygaster 

 semisulcatus, we can turn to the history of its use by British authors. 



For sixteen years after the publication of Clypeus semisulcatus, 

 that species was the only Pygaster recognized by name in Britain. 

 Indications that another species had been collected are to be found in 

 Morris (loc. cit., 1843), where P. semisulcatus is recorded from the 

 " Great Oolite " (really Inferior Oolite) of Gristhorpe, Yorks, in 

 addition to its original Corallian localities. It seems, however, that 

 very great confusion existed as to the generic character of the 

 Corallian Pygasters. Parkinson {Org. Rem.) referred to Clypeus 

 sinuatus specimens from the Coral Rag of Berkshire and Oxfordshire, 

 which were in all probability species of Pygaster. Conybeare and 

 Phillips ( Geol. Eng. and Wales) followed him in regarding C. sinuatus 

 as a characteristic fossil of the Inferior, Great, and Coralline Oolites ; 

 and, as late as 1850, Mantell, in republishing some of Parkinson's 

 drawings, emphasized the frequent occurrence of C. sinuatus in the 

 Corallian. It is true that species of Clypeus and Pygurus have been 

 found in the British Corallian, but they are extremely rare, so that 

 it is most improbable that these references actually apply to them. 



In 1844 Buckman(Murchison's Geology of Cheltenham), recognizing 

 the difference between the " Clypeus" of the Inferior Oolite of the 

 Cotteswolds and that of the Corallian, distinguished the former 

 species as C. ornalus, and in 1848 M'Coy (Ann. Mag. Nat. Hist.) 

 gave the name Pygaster brevifrons to a form from the Inferior Oolite 

 of Dundry Hill. The latter author followed Agassiz and Desor in 

 their identification of Clypeus semisulcatus with Pygaster umbrella 

 (M'Coy, loc. cit., p. 414), and recorded a specimen from the Coralline 

 Oolite of Malton under the latter name (id., p. 420). 



The first published reference of the name P. semisulcatus to the 

 Inferior Oolite species seems to have been that by Brodie (Q.J.G.S.) 

 in 1851. His identification of the Cotteswold forms with the 

 Yorkshire species was probably influenced by Wright, who, in the 

 following year (Ann. Mag. Nat. Hist.), united under the one specific 

 name forms from the Pea Grit, Great Oolite, and Coralline Oolite. 

 Forbes in 1854 (Morris' Cat., 2nd ed.) endorsed the identification of 

 these diverse species, still citing P. umbrella, Agass., 1839, as a 

 synonym. Two years later (Mem. Geol. Surv., Dec. Y) he repeated 

 the error, identifying actual specimens from the Inferior Oolite of 

 Gloucestershire and the Coral Bag of Paringdon under the name 

 P. semisulcatus. 



It is important to realize the prevalence of this belief in the 

 occurrence of the same species of Pygaster in the Corallian and 

 Inferior Oolite, because Phillips, when asked by Forbes to supply 



