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Jurassic Jumper
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Posts: 195
Reply with quote  #1 
Name: Birostrina concentrica.

Location: Found on the foreshore at Folkestone, Kent.

Range: Middle and Upper Albian (Cretaceous).

Diagnostics: These are inequivalved bivalves, with a highly convex form, that commonly occur as just a single valve, unlike the examples shown below. The umbo (beak) is highly curved, and shell ornamentation consists primarily of a number of approximately equidistant concentric ridges, hence the name concentrica. At Folkestone, many specimens still evince a nacreous (mother-of-pearl) coating, which represents the remainder of the original shell. The examples below are internal casts, but some nacre still remains, particularly on the leftmost example.

Size: Max diameter up to at least 4.5cm.

Reference: British Mesozoic Fossils (NHM) plate 57, ISBN 1-898298-73-4.

09012009202916.jpg 

(NB. scale in cm)

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Jurassic Jumper
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Reply with quote  #2 
Name: Plicatula gurgitis.

Location: Found in the slippages at Folkestone, Kent.

Range: Middle and Upper Albian (Cretaceous).

Diagnostics: An inequivalved bivalve, where the upper (larger) valve is moderately convex, and the lower (smaller) valve is even less concave than the other is convex. Shell ornamentation consists primarily of numerous alternating (equidistant) grooves and ridges running from the umbo towards the anterior shell margin, with various prominent serrations more-or-less evenly spaced along the edge of each ridge. Colouration varies somewhat, although shades of grey are commonest, as in the example below.

Size: Max diameter up to at least 4.1cm.

Reference: British Mesozoic Fossils (NHM) plate 57, ISBN 1-898298-73-4.

09012009212609.jpg 

(NB. scale in cm)


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"We try not to use the word insane, we prefer the term mentally hilarious..."



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Jurassic Jumper
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Posts: 195
Reply with quote  #3 
Name: Birostrina sulcata.

Location: Found on the foreshore at Folkestone, Kent.

Range: Middle and Upper Albian (Cretaceous).

Diagnostics: These are inequivalved bivalves, with a highly convex form, that commonly occur as just a single valve, as in the examples shown below. The umbo (beak) is highly curved, and shell ornamentation consists primarily of a small number of highly prominent, approximately equidistant alternating ridges and grooves running all the way from the umbo to the anterior shell margin. At Folkestone, many specimens still evince a nacreous (mother-of-pearl) coating, which represents the remainder of the original shell. The examples below are internal casts, but some nacre still remains, particularly on the central example.

Size: Max diameter up to at least 4.6cm.

Reference: British Mesozoic Fossils (NHM) plate 57, ISBN 1-898298-73-4.

10012009012405.jpg 

(NB. scale in cm)

-----------------
"We try not to use the word insane, we prefer the term mentally hilarious..."



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ThomasM

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Reply with quote  #4 

Name: Limaria gaultina



Range: Middle Albian



Location: Beach collected at Folkestone, Kent.



Diagnostics: Equivalved, elongate, rather flat form, with numerous
equisitant ridges running from the umbo to the anterior shell margin.
Fine striations also occur between the ridges, unfortunately not present
on the specimen shown due to it being an internal cast with no shell present. Even finer
concentric growth lines are also present, but may only be viewed with a
hand lens. Small wing-like projections also occur either side of the
umbo. The specimen shown is a phosphatic internal cast.



Size: Max diameter up to 4 or 5cm, but most specimens are much smaller. The specimen shown is about 1cm long.



Reference: "Fossils of the Gault Clay" Palaeontological Association Field Guide, plate 13, figs. 1 and 2 (2010).

P1010826j.jpg 

EDIT: Specimen prepped, picture updated.










Edited by ThomasM 2011-07-17 14:19:21

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