KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 2. 151 



Note on the colour of certain Cyathocrini. 



The specimens of Cyathocrinus longimanus and C. ramosus are always of a rich brown 

 colour; and t lus colour can hardly be due to the matrix, since other species in the same 

 matrix are of a yellowish colour. Whether, however, this colour would bave been retained 

 under difFerent conditions of preservation is uncertain. Similar instances are of coui^se very 

 common; tor example, soine species of Thysanocrinus from the Wenlock Limestone are of 

 a deep brown, sometimes almost black, while in the Lower Carboniferous rocks of North 

 America certain species tnay always be distinguished by their colour. In other cases a 

 dark colouring seems to characterise a whole genus as Dimerocrinus of the Wenlock 

 Limestone. Sometimes, on the other hand, the colour appears to be concentrated in parti- 

 cular regions of the crinoid, as the beautiful purple of the Apiocrinus root, which, how- 

 ever, is occasionally found in the upper columnals and in the crown. 



Experiments on a few fragments, chiefly of Apiocrinus, have failed to extract any 

 organic pigment such as the dusky purple »acid pentacrinin» of Prof. Moseley. This in- 

 deed was hardly to be expected, since so complicated a chemical compound could not 

 well be preserved by the ordinary processes of fossilisation. It has, on the other hand, 

 been possible to extract from this dark stereom, by dissolving it in hydrochloric acid, a 

 very large proportion of animal carbon *); and it appears that the presence of this in a 

 finely diffused state is what gives to the specimens their rich colour. The purest colour 

 so produeed is a purply black, but by the admixture of iron oxide this often becomes a 

 purplish, a reddish, or even a yellowish brown. No trace of manganese can be discovered. 

 The presence of large quantities of organic carbon can sometimes be detected in thin sec- 

 tions, by the aid of the microscope, especially in those träets where the meshes of the 

 stereom are more open, that is to say, where there was more organic matter in the living 

 animal; e. //. the musele träets of the stem of Herpetocrinus Ammonis. 



(ienerally speaking, then, the eonstant existence of a dark colour in any species 

 (wlien fossil) may be held to show that its stereom was not so fully developed, in pro- 

 portion to the organic strorna, as in allied species of a light colour. 



The presence of dark spöts on the arms, arranged in a definite pattern, as noted in 

 a specimen of C. acinotubus (57360 B. M. See »Brit. Foss. Crin. VIII,» p. 215) may pos- 

 sibly be the relic of sotne original colouring, since similar ornament is found in recent 

 forms. At the same time the above observations should render us very cautious in 

 ascribing the dark bands and patches, that are sometimes found in various fossils, to the 

 presence of an original pigment. It is quite possible that in many cases they represent 

 nothing more than the remains of the organic substratuin in or on which the stereom 

 was deposited. 



l ) Compare James Pakkinson, Organic Remains 4c, vol TI. pp. 1GG, 286; London. 1808. 



