NATURAL HISTORY SOCIETY OF GLASGO^V. 335 



be numerous on broken stems, but bore little evidence to explain 

 their nature to one ignorant of marine organisms other than 

 fossil ; and it may be said to be a comparatively recent revelation 

 that determined positively these sockets of crinoids. 



A. Is a type specimen of a socket of a crinoid, one may suppose, 

 from its rarity. It is an inverted cone, in a mass of calcareous 

 matter, wider than deep, with ratch-like work inside of the rim, 

 smooth sides, expanding at the bottom somewhat. Suppose a 

 pivot adapted to work in this socket attached to the bottom by 

 a ligament, and the fixture and movements may be thoroughly 

 comprehended. The pivot supposed above needed little farther 

 illustration, but since the reading of the former paper, that, too, 

 has absolutely been found. 



B. In this confused-looking specimen, covered almost with the 

 numerous basement portions of crinoids, there is one easily 

 observed to be dislocated, the socket and pivot being appositely 

 seen. Another shows the pivot, in situ, Avith ratch-work 

 corresponding to the socket. The demonstration, therefore, may 

 be pronounced satisfactory. 



Adventitious structures on crinoidal fragments. 



The stems of crinoids, in countless numbers, are often peopled 

 strangely, constituting, in a sense, a little world for study. A few 

 observations relating to these, restricted at present to Stenopora 

 Diastojjora, and Archaeopora, so plentifully found on the stems of 

 crinoidea in limestone strata of the Carboniferous epoch, may be 

 made, with the view of pointing out certain characteristic habits. 



1. Stenopora tumida. — Observing for long years this coralloid, 

 and carefully re-examining thirty specimens attached in clusters 

 to varieties of marine exuviae, but commonly to one side 

 of the larger and much worn or abraded stems of Poteriocrinus 

 crassus (specimen A), facts were noted which merit record. 

 Fifteen of that number present not only these clustered specimens, 

 but specimens with clusters which extend more or less to both 

 ends (specimen b). The clusters, in some instances, appear to 

 spring from several centres, which coalesce (specimen c). The 

 site of the clusters, their extent and behaviour, indicate that the 

 crinoids had evidently been dead, and partially buried, before the 

 little active colony took possession. Nine of thirty specimens 

 occupy only one side of the crinoid. Three specimens are 



