DE. T. DAVIDSON OX RECENT BEACHIOPODA. 125 



South Wales ; and l)y the ' Challenger ' Expedition near Sydney, attached to specimens of 

 JT'aldheimia Jlavescens, fonnd close to the shore. The Rev. Teuison Woods states 

 that the shell occurs in ahundance under stones at low water at Tamai Heads, also 

 oflP the south-east coast of Australia and New Zealand, and occasionally at Long Bay. 

 I have never seen any New-Zealand examples. 



Obs. — This small species is distinguishahle from Kraussina 2>isum by its much 

 smaller dimensions and comparatively stronger ril)s, as well as by some interior details. 

 It has been fortunate in retaining its specific name unchanged since first described. I 

 have through the liberality of Mr. Brazier been able to examine an extensive series of 

 specimens from half a line up to four lines in length. When very young the shell is 

 quite circular, with very few ribs, and these commence only at al)out half its length, 

 and extend to the lateral and frontal margins. On account of the shortness of its 

 peduncles the beak and umbo are often eroded and worn. In very young specimens 

 the septum and deviating lamellae are rudimentary and undeveloped. We are indcl)ted to 

 M. E. Deslougchamps for the discovery of the short accessory rudimentary lamellae that are 

 attached to the anterior lateral sides of the septum under the Y-shaped deviating lamellae. 



M. E. Deslongcliamps describes the interior characters of this and its allied forms 

 with considerable care and minuteness at p. 122 of his 'Etudes critiques.' He remarks, 

 that having been able to observe the calcareous appendages in adult examples only of 

 lLraussi)/a rubra, he can affirm nothing positive as to the manner in which they have 

 been produced, but that the disposition of these appendages — first in Kraussina 

 Davidsoni, and, secondly, in K. Lamarchiana — establishes points of transition so complete 

 between the genera Megerlta and Kraussina that he feels no uncertainty respecting 

 the position of these two genera in the zoological series, and that they certainly belong to a 

 single group. He states that the differences between the adult conditions of Kraussina 

 rubra and 3IegerUa truncata, although seeming at first sight very striking, disappear 

 or become much less conspicuous Avhen an adult Kraussina Lamarckiana is compared 

 \^'ith the transition-stages of Megerlia truncata, traces being found in K. Lamarckiana 

 of all the parts that constitute the calcareous processes in Megerlia [truncata). 

 M. Deslongchamps would therefore propose a subgenus Megerlina for the reception of 

 K Lamarckiana and K. Davidsoni, which, according to his views, constitute the passage- 

 forms between Kraussina rubra and Megerlia truncata. 



In his figure of K. Lamarckiana, M. Deslongchamps draws the hinge-plate simple 

 and concave ; but in my specimens it is quite similar to that of Kraussina rubra, with the 

 two eye-shaped scars due to the peduncular muscles ; and the only essential difference 

 that I can see is the presence of the short, broad, curved lamellaj that are attached to 

 the mesial septum under the upper forked deviating appendages. 



The diflerences and resemblances between the diff'ereut forms here alluded to will be 

 better understood by a glance at the figures in Pis. XX. and XXI. The brachial 

 aj^pendages in very young specimens of K. Lamarckiana are extremely small, as well as 

 the calcareous appendages for their support. 



M. Deslongchamps informs us, moreover [loc. cit.), that in Kraussina the spicula are 



17* 



