M. Agassiz on Fishes. 343 



the Atrypa galcala, Dalm., a new species of this same genus, one of 

 Plcurotoinaria, the Orlhocera pijrijannis, and many other fossils. 

 Tlie teeth of fishes have also been found in this formation, thout^h not 

 in great numbers, and lying most commonly in the upper Ludlow 

 rocks. No part of the body of a fish was ever discovered in this for- 

 mation till this present year, when the upper beds being removed at 

 Ludford, in digging the foundation of some houses, a heap of scales 

 wwe discovered, as also the rays of fins, and teeth completely broken, 

 lying huddled together, and forming a bed between the strata of sand- 

 stone which contain an immense number of Serpulje, also Leptcena 

 lata, and of other fossils ^^■hich characterize this formation. 



These fragments are too incomplete, to enable us at the present 

 moment to arrange them in a systematic table of classification. It 

 is, however, certain, that they do not present any specific analogy to 

 the fishes of the old red sandstone formation. The remains of the 

 fins belong to a different species of Ichthyodorulites, and the scales 

 appear to belong to different fishes of the family of Lepidoidians, for 

 their appearance is very varied ; the teeth, moreover, are less nume- 

 rous, and none have been found entire. The nature of these strata, 

 their disintegrated condition, and the fossils which they contain, have, 

 altogether, led Mr IMurchison to suppose that they have been depo- 

 sited in very shallow waters. Only a very few Ichthyodorulites have 

 been found in the lower Ludlow rocks ; and since Mr Murchison has 

 not collected them himself, he thinks that their presence in this sub- 

 division should be admitted with some degree of hesitation ; and the 

 more so, as they have not been found in the Aymestry limestone, 

 which contains such an immense quantity of organic debris, and 

 amongst others of the Petitamerus. 



The second formation, arising from the division of the greywacke 

 group, is composed of the fVenlock and the Dudley rock, which 

 swarm, so to speak, with corals, shells, and Trilobites. * Mr Murchi- 

 son divides it into two subdivisions : the upper comprehends the 

 Wenlock and Dudley limestone, which is a subcrystalline limestone, 

 highly concretionary, and of a grey or blue colour. It contains an 

 immense quantity of corals and crinoidea, — the BeJlerophon tenui- 

 fascia. Sow., theEiiomphalus nigosus and discuis, Sow., the Conularia 

 qnadrisulcala, Sow., a new species of PciUumerus, also of the Natica, 

 the Natica spirata, Sow., the Leptcena cugh/pha, Dalm., the Spirifer 

 linealux, Sow., and a new species of this last genus, the Terehratula 

 acneata, Dalm., the Produda depressa, Sow., many species of Ortho- 

 cera, the Asaphns caudalus, Brogn., the Calijmene Bhimcnbachii 

 Brogn., and other trilobites. This subdivision prevails remarkably 

 in the neighbourhood of Wenlock, in Shropshire, in Caermarthen- 

 shirc, at Dudley, and in Gloucestershire. The second subdivision 

 comprehends the Wenlock and Dudley argillaceous shales, which 

 are of a dark grey colour, rarely micaceous, and contain nodules of 

 earthy limestone. In these strata are especially found a variety of 

 the Asaphns caudaltts, the Cahjniene Blumenbaclin, a new specie's of 

 Liiigula, and a new species of Orlkis ; also the Cyrtia Irapezoidalis, 

 Dalm., a new species of Dellliyris, an Orlhocera, the Orlhocera an- 

 Jiulala, Sow., besides CrinohUa, &c. JMr Murchison has never found 

 the least trace of fishes in this formation. 



* Mr Murchison now names 'Jjis second formation the IVcnlock Limestone. 



