HARD WICKE 'S SCIENCE - GOSSIP. 



227 



Gerard Krefft, the curator of the Sidney Museum, to 

 Ceratodus, a genus till then only known by the fossil 

 teeth occurring abundantly in Triassic and Jurassic 

 strata. He also described it " as a gigantic amphi- 

 bian, and as allied to Lcpidosircn" the correctness of 

 which determination has been fully demonstrated by 

 the subsequent minute investigations of Dr. Giinther 

 and Professor Huxley, who have published exhaustive 

 memoirs on this subject. Two species of living 

 Ceratodonts are recognised, one named after its dis- 

 coverer, the Hon. William Foster, Ceratodus Fosteri, 

 and Ceratodus miolepis, distinguishable only by its 

 smaller and less ornate scales. These fish, known 

 locally as " flat-heads," inhabit the fresh and brackish 

 waters of the Queensland rivers, and "at night leave 

 the streams, and go out on the flats, among the reeds 

 and rushes, subject to tidal influence." Dr. Giiather 

 is, however, of opinion that they do not probably live 

 freely on land, as the limbs are too flexible and feeble 

 to support the heavy body, and considers that though 

 they may be occasionally compelled to leave the 

 water, they could not remain long in a lively condition 

 without it. The species, which range up to six feet 

 in length and twenty pounds in weight, appear to 

 feed exclusively on the remains of plants Myrtaccc and 

 GraiiiiucB, taken in a decomposing state. Tlie body 

 of Ceratodus is covered with large cycloid scales, and 

 the limbs are structurally identical with those of 

 Lepidosircn, but the axis and fringe are more dilated, 

 and the fin scales distinctly visible. The internal 

 skeleton, though of a more cartilaginous type, re- 

 sembles that of the mud-fishes, and the skull is partly 

 osseous. The anterior nasal openings are situated 

 under the lip, in front of the vomerine teeth, while 

 the posterior pair are placed in the cavity of the 

 mouth, a little before the maxillary ones. The den- 

 tition is essentially that oi Lepidosiren, slightly modified 

 to suit herbivorous diet, being adapted rather for 

 "cutting and crushing" instead of "piercing and 

 cutting." It consists of a pair of vomerine teeth and 

 two molars in each jaw, thus proving the correctness 

 of the views of Pander and Agassiz, who had assigned 

 that number of dental plates to the fossil forms of the 

 middle geologic ages. The respiratory organs are 

 twofold, as in Lepidosiren, but the gills are more 

 developed in Ceratodus, and when inhabiting clear 

 waters the fish probably breathes by them alone, the 

 true lungs only conaing into action when on the mud 

 flats, or living in turbid waters. The shape of the 

 body, the number, position, and structure of the fins, 

 the elements of the internal skeleton, and above all 

 the co-existence of a lung with gills, show how close 

 is the affinity between the Australian Ceratodus and 

 the mud-fishes of Africa and South America ; and 

 although the former approach less to the amphibian 

 type than the latter, it is obvious that in a natural 

 classification their place is side by side. 



( To he continued. ) 



THE HARVEST-BUG. 

 {Leptus autumnalis.) 



OF all the insects with which entomologists are 

 acquainted, few are more troublesome than 

 the tiny hexapod depicted in our sketch. In pro- 

 portion to its size, it has, perhaps, greater powers of 

 annoyance than any other insect indigenous to this 

 country. A moment's reflection on the part of our 

 readers will bring to their remembrance a host of 

 troublesome insects, but should they ever have been 

 attacked by an army of harvest-bugs, they will scarcely 

 need to be informed that, in proportion to its size, its 

 powers of punishment far exceed those of any other 

 of our indoor or outdoor tormentors. The flea 

 {Pulex irritans), the common bed-bug {Cimex lectu- 

 larius), and the gnat {Culcx pipiens) sometimes punish 

 us severely, but in considering this, it must be re- 

 membered that the smallest fully-developed specimen 

 of the smallest of these, namely, the flea, is at least 

 one hundred times larger than the harvest-bug. The 

 latter is, in fact, a near approach to a mathematical 

 point ? Three or four may be easily overlooked on 

 the point of a needle. 



As its name implies, this bug is found during the 

 months of harvest. So far as our obsei'vations extend, 

 its period of activity ranges from June to October ; 

 August and September being the months during 

 which it is most active. A period of drought appears 

 to contribute to its abundance and activity. In this 

 respect it is exactly the reverse to a similar insect, 

 said by Kirby and Spence to be found in Brazil, and 

 to abound in the rainy season. 



We believe that during the whole year this insect 

 makes its home in our fields and gardens ; the above 

 period being that of its activity. As we should 

 expect to find, this tiny creature has its preferences. 

 In tlie harvest-fields it seems to prefer those of wheat. 

 In our gardens, the French or kidney-bean plant and 

 the leaves of the currant-tree appear to be its paradise. 

 We have observed that whilst it may be found on 

 nearly every vegetable in a garden, it is always most 

 abundant on those above indicated ; the bean plant 

 being preferred to those of the currant-tree. We 

 fancy, loo, we hear our readers saying that the body of 

 man must be preferred to the plant of the Fi-ench 

 bean. This may be so, but it is a point we have not 

 yet been able to decide. Our experience thus far is 

 against the proposition ; for, unless the plant on 

 which the little creature exists is disturbed, we have 

 never known it to attack man, but the instant it is 

 interfered with, by walking through the harvest-fields 

 or brushing against the garden plants, it commences its 

 attack. Its weight is so infinitesimal, and its motion 

 so slight, that the body of man, sensitive as it is, is 

 not aware of the presence of the enemy until the attack 

 is fairly commenced. 



But, before proceeding further, it may be as well to 

 state that the harvest-bug has the power of adapting 



