510 C. T. Trechmann— 



the living chamber to be cleaned out and developed, it is seen to 

 agree very well in detail with the living chamber of the genus 

 Hijjpurites (see PL XX, Fig. 1). Though contending all through his 

 paper for the similarity of Barrettia to the palaeozoic corals rather 

 than to the mollusca, Whitfield, nevertheless, is content to retain 

 the generic name Barrettia, which was distinctly defined by 

 Woodward as belonging to a moUuscan structure. 



Whitfield recognizes three species among the Jamaican material 

 which was sent to New York by Mr. F. C. Nicholas ; these are — 

 Barrettia monilifera Woodward. 

 ,, multilirata Whitfield. 

 s-parcilirata Whitfield. 



The two first species were collected at Orange Cove or Haughton 

 Hall, near C4reen Island, the last only at Logic Green, in Clarendon 

 Parish, near the centre. of Jamaica. 



Barrettia cf. monilifera S. P. Woodward. PI. XIX, Figs. 2a, h. 



PI. XX, Figs. 1, 2. 

 1862. " Some Account oi Barrettia " : The Geologist, -p. 312. 



Description. — Several examples in my collection are apparently 

 referable to the type species as regards the number of the septa and 

 other features. The top valve is remarkably thin, and follows the 

 uneven contour of the surface of the lower or attached valve, which 

 is frequently curiously irregular and undulating. In large individuals 

 the surface of the upper valve is much eroded and battered or over- 

 grown with oysters or other shells, and the ornamentation thereby 

 obscured, but in younger specimens the decoration is often 

 preserved. It consists of a series of irregular saucer-like depressions 

 which are frequently elongated in a direction parallel to the margin 

 of the shell, and form a very irregular reticulate ornamentation (see 

 PI. XIX, Fig. 2a). The depressions correspond on the under side 

 of the top valve with peg-like projections, which fit into pits on the 

 surface of the lower valve. These pits are remarkably irregular in 

 size and distribution, some being 10 mm. deep, others quite shallow 

 (PI. XX, Fig. 1). In young examples of this species the decoration 

 of the sides of the lower valve is well shown, and consists of fairly 

 regular, sharply incised, but shallow sulci, which radiate from the 

 apex of attachment and pass up to the margin of the valve. Other 

 similar sulci are interposed between these some distance above the 

 apex, the sulci corresponding with the moniliform rays (PL XIX, 

 Fig. 2b). In young specimens there is an embayment of the margin 

 of the lower valve corresponding apparently with the original position 

 of the hinge-line, but this feature is lost in older examples where the 

 valve attains a circular outline. I could not detect any trace of 

 external grooves on the lower valve to correspond with the position 

 of the pillars, as is the case with most species of Hippurites. 



The spacing of the moniliform rays is very irregular and in places 

 they are much more crowded together than in others, and the shell 



