Miscellaneous. 505 



there are divisions in the clay corresponding to those so strongly 

 marked by their occurrence here. The Tetworth clay has long been 

 known to have an extensive southern development ; a portion of it 

 appears to have been mapped by the Geological Survey as Oxford 

 clay, just as in our district Mr. Lucas Barrett mapped it with the 

 Kimmeridge clay. 



MISCELLANEOUS. 



On the Larva of a Brachiopod. By F. Muller. 



In the 'Annals' for October 1860 (p. 310) we gave a short abs- 

 tract of a description of the larva of a Brachiopod observed by Dr. 

 F. Muller at Santa Catharina, on the coast of Brazil ; he now adds 

 some further details from repeated observations in the summers of 

 1859 and 1860. The larva appears to occur late in the summer, 

 from February to April. 



When the little animals are placed in good-sized vessels with pure 

 sea-water, they soon ascend slowly ; the slightly gaping shells stand 

 perpendicularly, the hinge-margin downwards ; dose to the anterior 

 margin the eight arms spread out horizontally like rays, with their 

 tips slightly bent downwards ; and the roundish knob situated be- 

 tween the uppermost pair projects beyond the plane of the arms. 

 In this posture they move slowly about near the surface. When 

 strongly shaken, or sometimes without any perceptible reason, they 

 retract the arms and close the shells, which then slowly turn over 

 and sink to the bottom with the free margin downwards. If the 

 arms be again protruded, the hinge-margin also again turns down- 

 wards. 



The duration of this state never exceeded five to six days ; and in 

 general the larvae adhered to the bottom or sides of the vessel in a still 

 shorter time. When they adhered to the sides, the mouth was always 

 directed downwards; the ventral shell was strongly drawn forward, 

 until its anterior margin reached or passed that of the dorsal shell ; 

 the transversely oval plate, previously concealed within the shells (the 

 peduncle), was protruded, apparently twisting round the notched 

 hinder margin of the ventral shell, so that its anterior margin became 

 posterior. For a day or more the animal remains contracted and 

 quiet ; then, the shells being slightly opened, the arms are half ex- 

 tended, and strike inwards, one or more at a time, just as in the 

 marine Bryozoa. 



In a few days new bristles appear at the anterior margin, in the 

 space left between the more delicate setae of the dorsal shell. In a 

 week the author counted twenty of these, mostly belonging to the 

 dorsal shell. The longest were - 8 mill, in length, straight, colourless, 

 0006 mill, in thickness at the base, terminating in a fine point, un- 

 jointed, and distantly feathered with fine lateral setae 0'02 mill, in 

 length. The principal change in the soft parts consisted in the re- 

 trogression of the organs of sense. The eyes had become broken up 

 into groups of about ten black points ; the previously spherical audi- 



