123 



HARDWICKE'S SCIENCE-GOSSIP. 



And further, authors appear to be at variance in 

 considering what forms are types, especially in regard 

 to the Anodons. Brown (1845) and Tate (1866) have 

 each represented a form of A. cygnea which I believe 

 is generally considered as the type, but Gray (1840, 

 frontispiece) has given a figure of a form of the so- 

 called Zellensis. I have seen the variety which is 

 represented by Gray's figure from two or three places, 

 but it does not seem to be as common as the larger 

 forms of Zellensis. Judging from the number ex- 

 amined there seem to be three forms of A. cygnea 

 that are common. These, in the order of frequency, 

 are (1) Zellensis, Genel ; (2) type of Brown and Tate, 

 and (3) the form called rostrata ; but between these, 

 and approaching one or the other, there are numerous 

 intermediates, which cannot with certainty be classed 

 under any of the recognised forms. The variety 

 called intermedia, figured by Brown, is more allied 

 to cygnea than io anatina. Mr. Rhodes, an industrious 

 Bradford collector, sent me a number of this variety 

 from a pond at Pudsey, near Leeds. I also got it 

 from the Rev. W. C. Hey, of York. The York shells 

 are very thin, agreeing with Brown's description. 

 The Pudsey shells are rather thicker and variable in 

 size and degree of inflation. Both are green, the 

 Pudsey shells being very bright and beautifully rayed. 

 Alder considered that this should be regarded as a 

 species ; Jeffreys does not mention it. I also had 

 this form sent from Staffordshire by Mr. J. R. B. 

 Masefield, of Cheadle, but the shell is a degree thicker 

 than the Pudsey specimens. Amongst Mr. Rhodes' 

 shells is a remarkable subtriangular form of intermedia. 

 The nucleus is nearly in the middle of the upper 

 margin, which slopes upwards from before and behind 

 — the hinge forming the apex of the triangle. Another 

 specimen has the valves unequal in length. This 

 variety, species, or what it is, seems to live at times 

 rather deep in the mud. In a letter, under date May 7, 

 1887, Mr. Rhodes says: "The enclosed shells now 

 sent were obtained from a storage dam which is 

 4 feet deep in soft mud. I find them about 8 inches 

 from the surface. There is about one foot of 

 water and no vegetation. The dam is well shaded 

 with trees. I obtained them by taking off boots and 

 going in, sinking at each step up to the knees in mud. 

 I had to put my arm up to the elbow in water and 

 mud to get the shells, and had to keep constantly 

 walking or otherwise I should have stuck fast." 

 Under date July 5th, he again writes: "The shells 

 keep very deep in the mud from 6 to 12 inches down, 

 so that they can only be got by going in knee deep 

 in the sludge and looking for the little holes and 

 depressions which indicate where they are." The 

 average size of intermedia may be about 2\ inches 

 from hinge to lower margin, 4 inches from side to 

 side, and if thick. 



In the Leeds and Liverpool canal, varieties of 

 Anodonta, both species, occur, which are brown in 

 colour, small, and not rayed. I imagined that ex- 



posure in dredge heaps, and lying dead in the mud 

 for some time, might change the colour of the epi- 

 dermis, but Mr. J. A. Hargreaves, of Shipley, near 

 Bradford, who collected some hundreds of specimens, 

 and who is an excellent observer, informs me that 

 such is not the case, neither does scalding of either 

 dead or living specimens affect in any way the colour. 

 Many of the shells, however, Mr. Hargreaves says, 

 are green when young. Many of the canal shells are 

 characterised by being much compressed. Some that 

 are 3.5 inches in breadth, more than 2 inches in length 

 from beak to margin, are less than 1 inch in depth 

 or thickness. In these the animal is exceedingly 

 small. The largest brown shells are 5 T 3 inches in 

 breadth and 3! inches in length. One specimen of 

 Anodonta anatina var. complanata, collected by Mr. 

 Hargreaves, contained a pearl of a yellow colour 

 about half the size of a pea. A monstrosity of A. 

 cygnea var. rostrata was collected by Mr. Rhodes from 

 a pond. The edges of the valves on the lower margin 

 are folded inwards for a certain distance, and the 

 posterior side of the shell is much pinched in at the 

 extremity. About twenty specimens of this deformity 

 were collected. The shell appears to be normal up to 

 the last period of growth. 



So far as I have been able to observe, the green 

 forms of A. cygnea run larger than the brown forms, 

 irrespective of locality. Some of the Bradford shells 

 are nearly black, and some that I have from a pond 

 at Rothwell Haigh, near Leeds, are of a dark slaty 

 blue colour, white on the umbones, smooth, saining 

 and faintly rayed. 



The form called by Jeffreys Anodonta anatina var. 

 complanata, should, in my opinion, be raised to the rank 

 of a species. The hinge-line is not elevated into a 

 thin sharp wing, the shell is not angulated in any 

 part of its outline as is typical anatina, and it is 

 brown in colour. The varieties radiata should be 

 suppressed, as rays of different kinds are common to 

 both species, and to many varieties, and are found on 

 shells of all sizes and colours, and from all localities, 

 being in short a part of the ordinary colouring. Rays 

 are most strongly marked on green shells. The 

 variety intermedia (Pfeiffer) should be introduced into 

 our handbooks, and made to comprehend Brown's 

 subrhombea, to which it appears to be closely allied. 

 The variety pallida, recorded by Jeffreys from the 

 West coast of Ireland, seems to be rare. I have only 

 once seen it mentioned in local lists, and that was in 

 a Birmingham list by Mr. Sherriff Tye. I have it 

 from Mr. Masefield, who got it in Staffordshire, and 

 from the Leeds and Bamsley canal procured by Mr. 

 J. YVilcoek. Mr. Masefield's is of a clear fawn 

 colour, Zellensis in form. 



The greatest difficulty in the study of the Unionida 

 is with young shells and with the numerous inter- 

 mediate forms. Jeffreys kept altering his views 

 as he became more and more acquainted with the 

 subject, and so will any one else that has continued 



