150 AXEL A. OLSSON 



Genus SP0IO)TLUS Linn6, 1758 

 Type species by subsequent designation, Spondylus gaederopus Linne. 

 Recent, Mediterranean. 



Shell large or of medium size, solid, pectiniform but usually deformed 

 due to fixation, the attachment is generally by the umbone of the right 

 valve. The lower or right valve is generally larger, more inflated than the 

 left with a high, triangular cardinal area. Ligament internal, lodged in a 

 deep, ventral pit, the external growth trace of which shows as a narrow, 

 deep slit or furrow extending upward along the cardinal area of the right 

 valve to the tip of the beak. Hinge line straight, each valve with two, 

 stout, crural teeth and their bordering sockets. The sculpture is principally 

 radial, formed by ribs or riblets of primary, secondary, and tertiary size, 

 often bearing pointed, fluted, or spatulate spines. On the lower valve there 

 is usually a tendency for the sculpture to become concentrically foliaceous. 

 Coloration white, purple, orange or red, the interior of shell cavity white and 

 porcellaneous, often with a wide, strongly colored marginal band. 



The size of the attachment area along the umbonal section of the 

 right valve seems to vary amongst different species, as well as greatly 

 controls its general appearance and sculptural development. In general, 

 the sculpture of the lower or attached valve is more strongly concentrically 

 foliaceous, as an aid in attachment, but usually the concentric folios are 

 replaced with spines as the edge of the shell rises and becomes free from 

 the substratum. Some species of Spondylus grow to a large size when adult, 

 their shell becoming much thickened and bored into by marine animals; 

 where such shells are common they may be gathered and burned in the 

 production of lime. 



Several forms of Spondylus occur in the Panamic-Pacific region and 

 to which names were given by the early authors; some of these forms are 

 merely color or growth variants. Considered in a conservative manner, all 

 the Panamic Spondyli could well be grouped together in a single, wide- 

 spread, plastic species, its main characteristics controlled largely by the 

 sort of surface to which it was attached, or if grown in a confined or in an 

 open space. Until the ecology of the Panamic Spondyli is much better 

 known than at present, the question whether there is one or several species 

 involved cannot be answered. For the purpose of this review, the following 

 arrangement is offered. 



Key to species of Spondylus 



A. Valves usually regular, pectiniform, seldom much distorted, the at- 

 tachment scar on the umbone of the lower valves of relatively small 

 size. 



1. Sculpture formed by rows of stout, spikelike spines, closely crowded, 

 the primary interspaces covered completely by secondary and tertiary 

 spines (each interspace has one central row of secondary and usually 

 four rows of tertiary spines, two on each side of middle). Coloration 

 a uniform orange or coral-red. 



S. princeps princeps 



2. Sparser surface sculpture, the interspaces wider and more open. Pri- 

 mary spines large, fluted or foliated at the ends and generally light- 

 colored, white or yellow. 



S. princeps leucacanthus 



