90 ON THE GENUS KRAUSSINA IN TASMANIA.. 



Other brachiopoda, calls attention to the presence of calcareous- 

 spicula in their mantle and its appendages. It is not alto- 

 gether certain that this is a reliable character for forming 

 large groups, and it has yet to be proved that it is of value 

 even for generic distinctions. From sections which have 

 been made for us by Mr. F. E. ^'urbury, of Launceston, we 

 observe that the fleshy substance of the oral arm in K. 

 Laniarcliiana is strengthened in a remarkable manner by an 

 interlocking mass of branching and denticulate spicula, often 

 of a staghorn form. These do not form a continuous net- 

 work, but with care can be disarticulated. Evidently this 

 internal skeleton, as it may be called, supports and fortifies 

 the arms, and is mostly found in the animals which have 

 only short brachial supports, the place of which they thus 

 ta^ke to some extent. 



From what we have gathered from our observations 

 detailed al)Ove, we are inclined to regard the smooth shell as 

 nothing more than a varietal form of Kraussina Lamarckiana. 



Kraussina AtJci7isoni. — Thia small shell, catalogued by 

 Tenison- Woods, was dredged by the Rev. H. D. Atkinson 

 in Long Bay, D'Entrecasteaux Channel. Dr. Davidson 

 says it is the only smooth Kraussina known to him, but 

 as we have just shown, K. Lamarckiana embraces a smooth 

 variety. Davidson has described the shell completely in his 

 monograph of Recent Brachiopoda (p. 127), and we need not 

 repeat what he has done so well. Several specimens have 

 been kindly placed at our disposal by the Eev. H. D. Atkinson, 

 and we have consequently been able to examine thoroughly 

 this little-known shell. The differences between its brachial 

 support, and that of K. Lamarckiana, may be summed up by 

 sayiua- that its lateral lamellae are on a horizontal plane, 

 instead of being directed slightly downwards, and the shape 

 of these is strap-like instead of being swollen as in K. 

 Lamarckiana. The shell canals, too, are unusually large, as 

 may be seen in our illustration. Unfortunately the animal 

 was al'sent from the valves entrusted to us, and consequently 

 we have to regret not being able to demonstrate the characters 

 of the spicula of this little-knovi^n species. That it is a good 

 species, and not a mere variety of K. Lamai'ckiana, the 

 material at our command is, as we think, sufficient to 

 establish. 



Explanation op Plate. 



Fig. 1. — Transverse section of shell canals of Kraussina 

 Lamarckiana, smooth variety, taken near surface of shell. 

 X 17. Ordinary light. 



Fig. 2. — Oral arm of Kraussina Lamarckiana xl7. The 

 photograph has been taken in polarised light, which illumi- 



